inductive substituent constants σji from olefinic geminal 1h, 1h nmr coupling constants

7iimMm Vol. 37, pp. 929 D 937 PnpaoD Pla Ltd.. 1981. Rinkd inoral hittin

INDUCTIVESUBSTITUENTCONSTANTSa; FROMOLEFINICGEMINAL'H,'HNMR

COUPLINGCONSTANTS

RUDOLF KNORR Institute of Organic Chemistry, University of Munich, Karl&. 23, D8ooo Mlncben 2, Germany

(Received in Gemany 23 July 1980)

Abtnrt--Theoretical and experimental arguments are presented supporting the postulate that olefinic NMR coupling constants *JHH are insensitive to /I-substituent influences on the okfink w orbital. A new set of substituent constants, ai, is proposed to measure directly the inductive substituent effect transmitted by o-bonds. The previously availabIe range of inductive substituent constants can be apprcciabIy extended in &is way. Comparisons of ur’ with other ohscrvabks and parameters for selected substitucnts are made as a test of consistency.

The quantification of substituent electronic effects by empirical linear free energy relationships is well established.’ Extensive work by many research groups has shown that a linear combination of polar (a,) and resonance (mR) substituent parameters constitutes a suitable approach.2 Resonance interactions, as transmitted through r-orbital systems, may be measured by gRo substituent constants which have recently gained im- provement and reliability from IR intensities.’ Of numerous efforts to apply new techniques for the re- evaluation of aI constants, only one’ may by singled out which enabled Taft and associates5 to meet the challenge of gas-phase acidities by calling on polarizabilityb effects.

Chemical bonds of o-symmetry might be thought to transmit the inductive effect (I,) of a substituent, thus providing an interpretation of aI substituent constants, However, contributions to err from hyperconjugation’ and field effects’.’ have been suspected on many occasions. Not even a rough measure of the pure LJ- inductive effect I, appears to have been generally accepted, although this would be of great value because of its relation to molecular electrical charges and their various consequences.

As a first step to provide such a measure at least approximately, the idea is presented here that the sub stituent dependence of okefinic geminal inter-proton coupiing constants ‘J,, might serve this purpose.

Theoretical models Geminal ‘H-NMR coupling constants 2J (HA, H”) of

protons attached to tetracovalent (sp’) C atoms are known to depend on the presence and conformation of adjacent a-orbital systems”*” (e.g. by hyperconjugation). Geminal protons at trigonal (sp2) C atoms in a terminal olefin 1, being held in a sterically rigid position, offer a much better model for the separation of s- and o-orbital effects. Conformational changes like decoup- ling of s-systems as in 2 are still possible but occur rather remotely and, therefore, mediated mainly by the P-bond.

*H, ,R B ,‘=‘,

H X

1 2

The theoretical dependence of 2J(HA, H*) on u and n interactions with the substituents X has been analyzed at difierent levels of sophistication. PGple and Bothner- By’2 in a lucid analysis succeeded in accounting satis- factorily for the experimentally observed trends without recourse to the olefinic a-bond; predominant interaction of increasingly electronegative p-substituents R and X with the antisymmetrical I~(CHZ) combination of u-orbitals results in more negative ‘J values. The same con- clusions were reached using the p-substituent as a perturbation at trigonal carbon,” and omission of r-effects proved successful also in ab initio calculations.” Similarly, n-contributions to olefinic 2J were found to be less significant than the o-bond transmitted part, using localized spin-orbital” and semiempirical MO theories,16 with substituent effects operating almost exclusively on the c-contribution.‘6*”

Consequently the change from a coplanar conformation like 1 to a perpendicular one like 2 should produce negligible variations in 2J. This had been verified”’ in the INDO approximation without commenV9 and is supported by experimental evidence to be given below.

Small dependence of ‘J on T charges and soloent. Attention is drawn to the surprisingly small variations of experimental 2J values in Table 1, as compared to the much wider total range (I2 Hz) in Table 2. The spectral representatio$“ of the 1,1&trimethylallyl cation indicates that ‘1 is smaller than the long-range coupling constant (entry 1 of Table I). Changing the total I charge by two formal units leads to ally1 anions2’-ti (entries 2-10) with only modest variation in ‘J, including solvent and cation effects as well as or-ally1 bonding in the complext6 of entry 9. Propene with 2J = +2.&I Hzf7 might be considered a reference. A direct comparison was made in entries 11-14 between l-azaallyl anions and their parent secenamines;te similar behaviour becomes evident from some vinyl ethers=” (entries U-17) and the enolateUZ2 of entry 18. it would not even be neces- sary to invoke small r-charge effects because the U- inductive influence of the charged atoms would operate in the same direction due to reduced electronegtivity.

Running through the usual range of lrclectron donor and acceptor p-substituents in styrene derivatives3%% reveals only minor changes of 2/, as shown in entries 19-21 of Table 2. About the same small variations are observed in entries 22-24 and 25-27 for compounds with

929

930 R. KNOFZR

Table I. Dependence of *J(H*, HB) in allyl-type compounds 1 on substitucnts R aad X. Signs of *I detemhd experimentally, inferred (in parentheses). or unspcci6e4l (in slashes)

rmtry ll x 25 [Ilzj tin, Solvent SOLIZ-CC

1

2a

20

9

4

5

0

5a

7b

b

9

10

1 la

1 lb

12a

12b

13a

13b

14a

14b

15

16

17

18

cm3

II

11

II

11

II

11

II

H

CH9

CH 3

CHj

II

II

cp5

C2H, ,

tcz;p Y

tC4Hy

‘gH5

‘gH5

H

H

Ii

H

@C(ClL& IL1.5)

%:2 (+)t.r+

0 Cl12 (+)2.8

8 ClICll 3 (+)3.4

~CIIciI 2 tc II ‘I ‘I

(+)l.L,

~c1rc 11 6 5 (+)3.2

Qc(cIr.Jc,l15 (+)3.5

@c(c6115)2 (+)3.6

WC,lf5), +3.6

QCH, (+)2.y

ec( c11g2 ca. (+)2

%IC H 6 5 (+)3.3

Nl~-cColI, 1 ICO.31

~N-cCbH1 1 +1.3

NHC& 0

eNC 11 6 5 (+)2.3

NIIC II b 9

0

eh.c II 6 5 (+)2.3

N”C6H5 0

GNC ,H b 5 (+)1.4

O-vinyl -1.6

0-iC4Hg -1.7

0- tC4Hy -0.1

80 +1.56

F5SbCX

L1+ ) 1’111,

K 4 , Ce* , 'I'lIF

K4 * TIIF

Li+, TIIF

Li+, THF

K*, NH.,

K4, NH3

IA+, THF

K4, ‘rw

Pd(I1)

K 4

* MI3

TIIF

Li4, THF

TIIF

Li+, TIfF

TIIF

Li+, THF

TIIF

Li+, THF

ccl4

=(CH&,

Li+, THF

ref.20

ref.21

rof.21

ref.21

ref.22

ref.23

ref?

ref.24

ref.25

ref.21

ref .26

ref.21t

ref.28

ref.28

r*f.28

ref.2b

rof.2t’

ref .28

ref .28

l-of .28

ref,2Y

=*f 30931 .

ref.30

ref 25932 .

reduced r-conjugation due to increasing steric hin- drance. This suggests that the r-charge alterations caused by the p-substituents are sensed at protons HA and H* not by n-conjugation but rather via o-orbitals (if not through space”).

Solvent effects on *J rarely exceed a 20.5 Hz variation,“‘” including even extreme casesm The reaction-field model provides a proper explanation in all cases by modulation of the B-substituent interaction with the CH, gro~p.~‘$” Temperature effects on 2J are extremely rare.”

solute values less than 0.09; that is, simple alkyl groups were excluded. Here and in the sequel the currently acknowledged a1 data were taken from various compilations. 2~s9 Although the sequence of substituent effects is of course independent of the choice of the origin, the calibrating substituents in Fig. 1 (filled symbols) define a straight line according to eqn (1) even with the imposed restriction that hydrogen should represent the origin as in most u scales.

7 and the a-kductioe efect. If n-interactions are in- significant, can the substituent influence on “1 be a pure acffect? Some further examples*” in Table 2 (entries MS) serve to demonstrate the much larger range of 21. For most of these substituents one would not expect the operation of a strong r-effect, whereas aI constants (if known) bear a certain resemblance to ‘l. Since both 2j and cl are proportional to energies, a linear relation between them might be postulated in a first attempt to deduce new (and desirable pure) inductive a{ constants. To this end, I adopted the policy of choosing some primary substituents (entries 35-42) whose OR” parameters are known with good precision’ but of ab

a,’ = 0.15(?0.005) * (2.4 - ‘1). (I)

It is encouraging to .observe that several other sub stituents (entries 33,34,43,44 and 45). corresponding to the very extremes of known uf values, fall close to the line of eqn (I) as shown in Fig. I by the open symbols.

Accepting the validity of eqn (I), one may venture to compute new a,’ parameters from the preceding and further&‘& coupling constants of olelin derivatives 1. A large but somewhat contracted series is shown in Table 3 where the entries have been sequenced so as to arrange the key atoms according to groups of the Periodic Table.

Correlation with other obsembfes. The internal CCC

932 R. KNO~R

LO-,

00

0.0 - 45 I 0.6 _\\\\\ 44 0

42

61 43 \

41

l 40

0.4 - \ 39 38 37

l

\

36

0.2 - 1 35

'II, 34

33

O- b._

\ 00

,-0.2 - \ I I I

-4 -2 0 2 4 *3 IHtl t

Fig. I. !kkcted literature values of aI constants as a calibrating function of coupling constants ‘1, with entry numbers from Table 2.

123-

I 12l-

d

119 -

117 - 4

158 130 0,

0 127

118 78

117 116

L -I 49

113 ' I I I I I 1 I J -0.8 -0.G 0 0.G 0.8

6; F

Fig. 2. hanuclear angles &C,&), in degrees, of l-substituted benzenes as a function of 0:.

Inductive substituent constants V: 933

transfet”‘“vb as “observables” show a reasonable relation to ai even though the interplay with P-charges must be allowed for.

DWUSION

The usual aI constants, if used in a dual parameter approach, provide daluable correlations of observables like chemical shifts, equilibria, and reaction rates which depend on differences of electronic energy in two states. That is, uI successfully incorporate polarization, electrical field, and hyperconjugation effects.

The ai parameters derived from 2J in the single parameter relationship of eqn (I) do not represent another variant to replace old uf values but are fundament- ally different quantities. They measure the substituent’s influence on the electronic ground state directly (analo- gous to new uRo values’) by a very small perturbation rather than by drastic electrical changes like ionization; the observable is the substituent-modulated magnetic (spin-spin) interaction of hydrogen nuclei with the u- bonding electrons. The present hypothesis does not im- ply that ?r and other effects are unimportant for the magnitude of 2J; it rather assumes that 21 differences should prevalently be influenced by differences of u- inductive /3-substituent effects. It is conceivable that other mechanisms contribute and magnify the observable *J up to useful sensitivity; they cannot be excluded unless they have structural (e.g. conformational) dependencies different from I,. Be this the case or not, applications of u,’ to observables containing electronic state changes are likely to meet with failure.

The quality of a,’ hinges upon the reliability of 2J values. Comparing results for the same compounds from different sources, it is not unusual to spot uncertainties of at least 20.1 Hz, corresponding in favourable cases to Au,’ cu. 20.02 and sometimes much worse. In order to avoid any bias and to show the necessity for eventual further testing, no selection of literature data was made with respect to experimental quality (or to compatibility with our model).

Since I, should be a short-range property related to local charges, one expects the key atoms in B-position to set the scale of u,‘. Secondary substituents at the key atom and occasionally also specific solvent effects may cause some variation. A glance at Table 3 verifies these expectations. For example, inspection of CN (u,’ = 0.22), NO, (0.63), S02R (ca. 0.45), and OR (cd. 0.63) provides a convincing illustration and furthermore demonstrates that electrical dipole moments are not of primary importance since the group moments’32 for the first three substituents are fairly similar but much larger than for the last one. Field effects parameters P cor- relate poorly with u13.

A comparison of u:~‘~ with aI’ reveals significant deviations, as expected. The new Us” parameters3 (valid for mono-substituted and meradisubstituted benzenes) offer the opportunity of returning to original ume,. data” as primary experimental evidence. The dtierence a,@ - uR” should5’*‘” provide a “corrected” set of polar constants and turns out to be in excellent agreement with the following a: parameters: Entries 54, 58, 60, 105, 114, 123, 127,143,146, 150 and 159-161. In other words, umu is efficiently corrected in these cases by OR” for all those substituent influences which cannot be measured by Us’. Serious increases ( > 0.11 ur units) are found in ul for t-butyl (entry 77) and fluoro (158), correspondingly serious reductions for cyano (103), trimethylsityl (1 IQ,

oxide (142), sulfoxyl (152) and sulfonyl (152). It is to be noted that a,‘, umeu - Us”, and Grab’s”’ parameter uIq, but not uI give the same ordering of Br > Cl > I; fluoro appears much more aelectron attracting if measured by g,’ as compared to umeu - uRo. Cyano falls rather short of the hitherto accepted strong c-acceptor behaviour; its r-acceptor character may have been underestimated and, indeed, appears somewhat controversial.3*‘3s*‘)6 Another explanation would assume a field effect contribution to ame,,, which does not equally operate in u13 and is not corrected for by uRo. However, trimethylsilyl has also been noted to give unexpected relsults in the same sense.13’ The negatively charged oxygen (142) in the enolate is seen to act only weakly u-electron withdraw- ing, in agreement with ab initio calculations.‘38

Me (58) and/or Et (60) groups are stronger u-acceptors than hydrogen on the a;, a,,,., - uRo, u,~‘* and uIq scales;‘y theoretical evidence’3’b-d points in the same direction. Neither the “inductive” nor the “Baker- Nathan” order13’ is obeyed in the alkyl sequencing of entries 58, 60, 65, 70 and 77, t-Bu being the strongest u-acceptor in this series. This reversed order, compared to the ul sequence, M is not necessarily incompatible with suggestion’ that alkyl induction and polarization have very nearly the same structural dependencies. However, molecular polarizabilitf” can hardly be responsible for the positive a,’ values since there is no net electrical charge to be stabilized in 1.

The apparently strong u-acceptor character of the transition metal complexes in entries 63,79, 141, I45 and 148 had been supported by a 2J sign determination only in the first case; it is furthermore uncertain whether these moieties can still be regarded as &substituents. The synthetically valuable, high nucleofugicity of imidazolyl-(1) in acylation reactions”” is seen from entry 128 to parallel its strong u-acceptance, comparable to chloro (entry 159).

Hybridization has been suggested” as a factor in addition to electronegativity determining 2J. Some of the very few estimations of the terminal CH, angles indicate quite similar values (cu. 120”) for the vinyl halides.‘42 The large change of ui towards ethylene (angle cu. 118°)‘43 and the smaller further change towards trivinyl- borane (angle 104e)‘u also suggest that hybridization is an inferior factor. This CH, compression by electron releasing #I-substituents is borne out by calculations on the vinyl anion.“’ Since the corresponding increase of ‘J is completely contrary to the angular dependence which was repeatedly ***“’ predicted by the otherwise successful theoretical”’ treatment, we conclude that hybridization effects are overrun by substituent influences also in the computational approach.

NMR coupling constants are generally dominated by the Fermi contact mechanism and hence a priori depen- dent on u-electron densities.z9*‘46 Therefore, a rough correlation of 2JHH with other types of coupling constants like ‘JCH14’ is often found, and a higher electronegativity of alkyl than of hydrogen may be inferred.lq

CONCLUSION

Theoretical and experimental considerations suggest a single-parameter eqn (I) as a first approximation to quantify u-inductive effects I, It is recognized that experimental and interpretative refinements of this sim- plistic approach may be inevitable. If subsequent pro- gress corroborates the proposal, *JHH may turn out to be

Tab

k 3.

u{

valu

es of

sub

stit

uent

s X in

1.8

9 co

mpu

ted f

rom

cqn

(I).

‘v

= vi

nyl,

*cyc

looc

ta-I

$5,7

-tet

nren

-l-y

l, ‘or

+

0.21

for

‘I =

tl

Hz,

‘an

d an

thr-

l-y\

, ‘an

d ph

enan

thr-

Pyl

, pyren-I-yl,

chry

scn

-Gyl

, ho

cyan

ide

and

its

CO

W)

com

ple

x, ‘

if

2I

neg

ativ

e, ) y

HJ.

M),

‘(~0

.03)

. ~(t

i.05)

X

in

I

6;:

Sou

rce

Ent

w

(R =

H)a

) of

2J

46

47

48

49

SO

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

If

JJi (

=I

Li (

Et2

0)

bB

r

Hg

-v

E&

oo

CC

K3

HEBr

m2

Alv2

01v2

Ma,

)2 CB

3

CH

2K

C2H

5

CR

CC

H3

CH

=CH

2

CH

=CH

2/F

e (CO) 3

CR'-CHR'

n-Alk

CH2CH(CH3J2

CH2C(CH&

CH2CH-CH2

CH

2C6H

5

CH

(CH

3)2

CH

f t-C,.H_)_

0

-0.7

8

-0.7

1

-0.7

5

-0.7

6

-0.1

7

-0.0

9

ea.-O.05

-0.26

-0.5

9

-0.2

6

-0.3

5

+0.0

5

-0.0

0

l 0.

07

ca.+

O.O

2

+o.

10

+0.7

2

+0.0

6

ca.+O.Oy

+0*0

5

0

+0.0

7

+o.o

a

+o.

10

-0.0

3

ref

43.4

6 .

ref

25.4

0 .

ref

60,6

1 .

rbf

40.4

1 .

ref

41+6

l

rOf:

62

ref

63a

.

ref 63a

r.f:63b

ref.62

mf.64

r.f.64

ref.27

ref.21

rsf.27

ref.65

ref

47.4

8

ref:66

ref

47,4

a .

ref

27t4

9

ref:67

ref.67

ref.68

raf.50

ref.67

ref.67

Entry

X in ;

source

(R I R)a)

of 2J

lo4

105

106

107

108

109

110

111

112

113

114

115

116

ll7

118

c ( O

CH

, ) C

H2

CO

-;A

lk

CO

CH

=CH

2

CO

C6H

5

CO

C(C

H3)

3

coN

R;

C02

Alk

, C02H

co2co-v,

COF

furyl-(2)

thienyl-(2)

CF3, COCl

ccl3

S+(CH&

siv .-j' warY$

GSV 3'

Ge2

V5

119

120

121

122

123

124

125

126

127

128

129

Ge(C6H5),,, SnClR:

Snv 3' Sn(CgH5)3

PbR

’ 3

%R

’

NH

R’,

NR;

carbazalyl-(9)

NC ')

NC0

*N(C

H,)

, imidazolyl-(1)

NR

7CO

R2,

N

(CO

H’),

+0.08

+o.18

40.15

+0.01

-0.01

ca. -0.13

ca.4

0.09

ca.+

0.24

40.15

40.24

40.3

3

40.43

-0.20

-0. I

a

-0.0

9

0

-0.12

40.06

40.17

40.3

6

40.4

8

40.4

3

40.3

8

41.0

0

40.60

40.36

r*f .4

7 ra

f.25.

aoa,

aq

=*f

49.8

3

r*fI

a3

ref.8

3

ref.4

9

ref

49.a

ob

.

ref

49.8

5

,.,:a4

ref?

ref

78.4

9

ref

149

ref

43,8

6 .

refB

Oa

,81

.49,

86,8

7 .

ref

49.8

7 .

ref

49.8

7 .

ref

25.4

4.62

,87,

88

.

ref. 4

9.87

ref,2a

ref

2a,4

9d9

.

ref

2514

9 .

ref.90

ref.49

ref

54.5

5 1

ref

25,4

9,91

.

ref

25*4

9.7’

~*90

.

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

94

97

98

99

100

101

102

103

C-C

3H4H

’ ca.+0.12

C-C6Hll

+0.07

c-C6H9-:;)

+b. 1

5

c-ca

n7

+o.

16

CW

3)3

+o.

15

v5

+0.2

0

CpH

5/C

r(C

0)3

c) c

a.+0

.51

C6H

4Har

-(

2)

+o.

20

C6H

4A’k

-(2)

ca.+

O.

12

C6H

3A1k

-(2.6

) ca

. +0

.03

C6H

2(C

H3)

3-(2

’4.6

) +0

.02

anth

ryl-(

2)

ca.+

0.36

naphthyl-(1)

ca.+O.Pl

naphthyl-(2)d)

ca.+0

.14

anthryl-(9)')

ca.+0.06

pyridyl-(2)

+O.ll

Pyr

idY

l-(3)

+0

.22

pyri

dyl-(

4)

+0.2

4

CH28n(CH2CH-CH2)3

+0.06

CH2CN

ca.+

O.21

CH2NR2

ca.+O.O8

CH2N02

+0.25

CH2OH

+0.10

CH20CH3

+0.06

CH2P

l 0.13

CH2Cl,

CH

2Br,

CH21

+0.18

cfio

+0.21

CH(OCH3)2

+0.08

-2

+o. 26

CHC12

k.32

CN

d.22

r,f.7

0*7’

ref.4

9 ref. 4

9 ref. 4

y ref 25.72

.

..f.33-35

ref.73

rwf.35

ref.35

rsf 25.35

.

ref.35174

ref.75

ref.75

ref,75

redf.75

ref.76

ref.76

ref.76

ref.44

,,f.5l

=*f 49.77

.

ref

.53b

ref.4g

ref.52

ref.78

ref.'om52

r.f.79

ref.s2

ref.78

rrf.52

,&9,37,8Ob-82

131

Pv*, PR;

l 0.06

ref “Y-92

.

132

%y15)3

+0.35

ref.Y2

133

P(O)R;, P(S)R;

+0.11

ref 49.93

.

134

PC

(OC

2H5)

2 +0.02

ref

W,Y

~

135

PCl2, PDr2. PSC12

+0.32

.PA

136

ASV2, *sn;

+0.11

rd.49

137

*..(c6115)3

+0.36

ref.95

138

Sbv2

+0.05

ref?

139

o"g) ,

O

C2H

5, OC4"Y

+0.63

ref96,30,3r.1w.25

.

140

OC

l13

+0.6a

ref

29-3

1 *Y7

.

141

0CH2CF3,

OR/Fc(CO),,

+O.t)l')

ref.Y6b'98

142

OLi

+0.13

ref 25.32

.

143

OCHR;, Oaryl

ca.+

0.57

r*

f 49

.99

.

144

0S@H3),

ca.

+0.3

6 ref.98

145

0Si(CH3)3/Fo(C0)4

+o.t

!+)

ref.

98

146

OOCH, OOCR'

+0.60

rsf

100,

?4,4

9 .

?47

00CSC6H5,

OOCNHR'

+0.519)

ref."'

148

OOCN

HCH3

/Fe(

CO

)4

+O.

96&j

ref.98

149

OPO(OR1)2

+O.?l

ref.4y

150

SR', S(C6H5)-Nary1

+0.36

ref2

5,49

,102

, 10

3 .

151

SC(CH3)3

to.20

ref 25,102

*

152

S(0)CH3, S02R1

40.4

3 re

f 49

~25

.

153

so2-

v,

S02C

4F9

+0.4

8 re

f 70

4~25

154

so2N

R;

+0*3

9 re

f:49

155

S03H

+0

.5

rsf.

lo5

156

S020R1

+0.47

ref.4g

157

SF 5

+o.

42%)

re

f. lo

6

158

? +o

. 84

h)

,,,*29

,37.

49,9

9

159

Cl

+O.

58’)

r,f,2

9137

,49,

99

160

Br

+0.6

3’)

,,f.2

9.37

.49.

99

161

I l o.

514k

) r,f

*37r

49,9

9

9% It. KNORR

one of the very few observables which measure Z, cor- rectly. Its use is restricted to terminal olefinic derivatives 1 (as opposed to ketenes and cumulenes) but applicable to most or all fi-substituents.

The ‘H NMR spectra of several compounds have been checked for the sign of the olefinic ‘&,, coupling constants by INDORIa experiments with the added advantage of assigning hidden spectral lines.“O Computer simulations of the vinyl spectral parts (6OMHz) served to co&m the analyses; numbers in parentheses indicate the uncertainties in the last digit. Anhydrow diethyl ether and THF were distilled from Na!benzophenone.

1.1.Dfphenylolly1tihium. Entry 7b (R. Lehmann). l,l- Diphenylpropene, too weakly acidic to react with lithium diiso- propylamide. was quickly deprotonated by I-phenylvinyl- lithium’j’ in [42THF. ‘H NMR spectral parameters equalled those of the potassium salt in ammonia,% except for olefinic ‘Iti = 10.9 Hz; 2.! = t3.6 Hz by INDOR.

2.Lithio-propme. Entries 30 and 31 (Dr. E. Lattke). 2. Bromopropehe was prepared”* from 2-methylproper@ acid and had b.p. 46.5-48” (Lit. If2 47-49”). The lithium compound in diithyl ether was obtained by 2h stirring with Li ribbon; ‘H NMR agreed with lit.”

The solvents were removed at 0.01 Torr and the residue dissolved in THF to give a stable soln. ‘H NMR 6 5.92 and 5.02 (2 dq, IJ=7.5, ‘I = 1.5). No spectral changes occurred upon cooling to -62” in both solvents.

Viny&?&n. Entries 28 and 47 (Dr. E. Lattke). From tetravinyltin’53 and BuLi in pcntawa evaporated and redis- solved in mflHF; ‘H NMR (simulated) 6 7.249(l) (H- I), 6.6641) (H - 2, tmns), 5.921(l) (H - 2, cis), 21 = + 7.56(9), ‘I= +18.81(9) and +23.98(9); no spectral change at -47”. Solns in diethyl ether and in C& with 1% of THF showed identical distances within each multiplet.

3.3.&ncthyl-1-butnc, Entry 77. ‘H NMRn verified with 2J= t1.37 by INDGR.

2’,6’-13imethyls~yttte. Entry 82 (Dr. E. Lattke). ‘I= t2.4 by INDOR.

2.Vinylpyridine. Entry 88. 21 = t1.66 (courtesy of Prof. T. Schaefer).

Buten-3-one. Entry 105. ‘H NMR (CQ) 6 6.263(5) (H- 2), 6X9(4) (H- 1, cis). 5.827(2) (H- 1, fruns), ‘I = t17.4(2) and +10.7(2), ‘I = +1.2(2).

7’etrauinyl~in. Entries 34 and 120 (R. Mertz, R. Lehmann). B-p. 72”/38Torr (Lit.15’ 67-70”/28Torr), 21 =+3.2(l) verified by IN- DOR (Lit.” 3.7, Lit.” t 3.14).

N-Vinylcnrbmde. Entry 124 (P. I.&w). ‘H NMR (CCL) S 7.095(2) (H - l), 5.730(2) (H-2, cis), 4.941(2) (H -2. frans). ‘I = t 15.7(2) and 9.3(2), 21 = -0.8(l).

N-Vinylimtizole. Entry 128 (P. Uw). ‘H NMR (CQ) 6 6.887(l) (H- I), S.lSl(l) (H - 2, cis), 4.7165(9) (H-2, trans), ‘I = -1.58(7), ‘I = +9.13(8) and +15.82(8).

N- Vinyl-2-pynvlidonc and N-acetyl-N-vinylaniline. Enby 129. ‘H NMR (CO,) ‘J < 0.3.

Nifmetlrcne. Entries 43 and 130 (Dr. P. DvortSak, E. Riipple). Prepared from 2-nitroethanol and phthalic anhydride.lY A rela- tively well-resolved ‘H NMR spectrum could be obtained in DC& to solve the peculiar discrepancies of the literature data”” by INDOR: 2J = -1.8.

Butyloxy-ethene. Entry 139, 21 = -1.8 by INDOR and simula- tion.

Lithium ethanolate. Entries 18 and 142 (P. Lbw). ‘H NMR” verified except for positive ‘J by INDOR.

Pmpylthio-efhene. Entry 150 (H. Graf, R. Brtickner). ‘H NMR (Ccl,) 6 6.229(2) (H - 1). 5.077(l) (H - 2, Imns), 4.974(l) (H - 2, cis), ‘I = +10.1(I) and +16.5(l), *I = -O&l).

Plunylthioerhene. Entry 150 (H. Graf, R. Briickner). ‘H NMR CCCW 6 6.425(2) (H - l), 5.234(2) (H - 2, frans), 5.221(2) (H - 2, cis). ‘I= +16.7(2) and +9.6(2), 2I = +0.0(2) by INDGR (compare Ref. [ 1021).

t-Eutylthio-ethene. Entry 151 (H. Gmf, R. BrUner). ‘H NMRlm (CC&) verified with zJ = +1.1(2) by INDOR.

Phcnylsuljonyl-rfhenc. Entry 152 (M. Fahimi). ‘H NMR (Ccl,) 6 6.644l(2) (H - l), 6.412(2) (H -2, cis), 6.003(l) (H -2, trens). ‘I= t 16.6(l) and +10.0(l), ‘I= -0.4(l).

NonoPuorobutylsulfonyl-ct~mc. Entry I53 (Dr. K. Lapin@. ‘H NMR ([D&enzene) S 6.022(2) (H - 2, cis), 5.837(l) (H - 1, long- range coupling to ‘pF), 5.329(l) (H - 2, tram), ‘I = 16&l(8) and 9.8(2), 25 = -0.8(3); ‘H NMR”’ (Ccl,) 6 6.7 (m).

Acknowledgemenls-The author is obliged to those of his col- leagues and students (named in the experimental section) who took part in the syntheses and/or NMR analyses, and to Mr. H. Huber for taking care of the HA#IL spectrometer provided by the Stiftung Volkswagenwerk. Encouraging comments by Prof. M. Barfield, J. Gasteiger, T. Schaefer, and S. Stemhell, as well as support by the Fends der Chemischen lndustrie are gratefully acknowledged.

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(1957). ‘%. D, Buckley and C. W. Scaife, I. Chem. Sot. 1471 (11147). r5sK. Laping and M. Hanack, 7’eWtedrrm Letters 1309 (1979).

inductive substituent constants σji from olefinic geminal 1h, 1h nmr coupling constants

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