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Addition of Allylic Boronates to Carbonyl Derivatives
Yuta Takenouchi
Contents
γ-alkoxyallylboronates (1981)
L.A. catalyzed allylation (2002)
R. W. Hoffmann
D. G. Hall
H. C. Brown
W. R. Roush
diisopinocampheylboranes (1983)
BR1
R2
BR1
R2
O
OCO2
iPr
CO2iPr
Tartaric acid esters (1985)
B
RO
HOR
OR
Sc(OTf)3
BMeO O
OⅠ. Introduction - Character of allylboronates - Mechanisms for diastereoselectivity
Ⅱ. Asymmetric allylboration
Ⅲ. Lewis acid catalyzed allylboration
Ⅳ. Recent researches
Ⅰ. Introduction - Character of allylboronates - Mechanisms for diastereoselectivity
Ⅱ. Asymmetric allylboration
Ⅲ. Lewis acid catalyzed allylboration
Ⅳ. Recent researches
C‒C bond formation
Allylation of Carbonyl Groups
BrPhCHO
Ph
OH
Cr(II) salt.
>95:5 dr
R1
OH
R2 R3
O
R1
OH
R2 R3
MLn
R1 H
O
R1
OH
R2 R3
H
OR1
OH
R2 R3
O
O
R1
O
R2 R3
aldol reaction product
Okude, Y.; Hirano, S.; Hiyama, T.; Nozaki, H. J. Am. Chem. Soc., 1977, 99, 3179–3181
Yamatnoto, Y.; Yatagai, H.; Naruta, Y.; Maruyama, K. J. Am. Chem. Soc.1980, 102, 7107-7109
Hoffmann, R. W.; Zeiss, H. J. Angew. Chem. Int. Ed. 1979, 18, 306–307.
B(pin)PhCHO
Ph
OH
96:4 dr
Sn(n-Bu)3PhCHO
Ph
OH
BF3·OEt2
>90:10 dr
▪Diastereoselective allylation▪C‒C bond formation with allylmetals
▶ Developed since the 1970’s
Blais, J.; l'Honore, A.; Soulié, J.; Cadiot, P. J. Organomet. Chem. 1974, 78, 323–337.Li, Y.; Houk, K. N. J. Am. Chem. Soc. 1989, 111, 1236–1240.
Brown, H. C.; Racherla, U. S.; Pellechia, P. J. J. Org. Chem. 1990, 55, 1868–1874.
▪Allyl silane, Allyl tin reagents
SiMe3R1
O
R2
TiCl4 OH
R1 R2
SiMe3
OH
R1 R2
櫻井-細見反応
Allylation with Allyl Metal Reagents
MLnR1
R3O
H
R2
R3
OH
R1 R2R3 H
O
R1
R2
MLn
L.A.
MgBrLi
▪Allyl lithium, allyl Grignard reagentsProblems ▶stability of reagents ▶α,γ-regioselectivity
Closed Transition State Open Transition State
✓ no added Lewis acid necessary ✓ proceed via rigid chair-like T. S. ✓ diastereospecific, diastereoselective
✓ require Lewis acid activation ✓ proceed via open T. S. ✓ not diastereospecific
MLnR1
R3O
H
R2
R3
OH
R1 R2R3 H
O
R1
R2
MLn
L.A.
Allylation with Allylboronates
Hoffmann, R. W.; Niel, G.; Schlapbach, A. Pure Appl. Chem. 1990, 62, 1993–1998.Gennari, C.; Fioravanzo, E.; Bernardi, A.; Vulpetti, A. Tetrahedron 1994, 50, 8815–8826.
Omoto, K.; Fujimoto, H. J. Org. Chem. 1998, 63, 8331–8336.Pietruszka, J.; Schöne, N. Synthesis 2005, 2006, 24–30.
▪Allylation with allylboronates (allylboration)
B
RO
H
R
OOR
OR
B(OR)2
R
O
H
B(OR)2
R
OHH+
Boration
Allylation
Closed Transition State Open Transition State
activation of the carbonyl group
✓ no added Lewis acid necessary ✓ proceed via rigid chair-like T. S. ✓ diastereospecific, diastereoselective
✓ require Lewis acid activation ✓ proceed via open T. S. ✓ not diastereospecific
Reactivity of Allylboronate Reagents
Kramer, G. W.; Brown, H. C. J Organomet Chem 1977, 132, 9–27.Hoffmann, R. W.; Zeiss, H. J. J. Org. Chem. 1981, 46, 1309–1314.
Brown, H. C.; Jadhav, P. K.; Bhat, K. S. J. Am. Chem. Soc. 1985, 107, 2564–2565.Ramachandran, P. V.; Pratihar, D.; Biswas, D.; Srivastava, A.; Ram Reddy, M. V. Org. Lett. 2004, 6, 481–484.
▶Low Lewis acidity of boronates
▶ Lower reactivity
BOR
ORR2
R1
R3
Sterically hindered R
EWG (eg. CO2R)
BOR
ORallylboronates
(11B σ~30 ppm)allylboranes
(11B σ~70 ppm)
BR
RLewis acidity
Nucleophilicity
B RR
B BO
OBO
O
Isomerized at rtB-crotyl-9-BBN Pinacol crotylboronate
Easy preparation of E or Z isomer
Ⅰ. Introduction - Character of allylboronates - Mechanisms for diastereoselectivity
Ⅱ. Asymmetric allylboration
Ⅲ. Lewis acid catalyzed allylboration
Ⅳ. Recent researches
B(pin)
RR
RO
B O
O
PhH
A1,3-strain
H
R
Impact of Substituent at α-Position
Tsai, D. J. S.; Matteson, D. S. Organometallics 1983, 2, 236–241.Hoffmann, R. W.; Dresely, S. Tetrahedron Lett. 1987, 28, 5303–5306.
Hoffmann, R. W. Pure and Applied Chemistry 1988, 60, 123–130.Carosi, L.; Lachance, H.; Hall, D. G. Tetrahedron Lett. 2005, 46, 8981–8985.
Fang, G. Y.; Aggarwal, V. K. Angew. Chem. Int. Ed. 2007, 46, 359–362.Althaus, M.; Mahmood, A.; Suárez, J. R.; Thomas, S. P.; Aggarwal, V. K. J. Am. Chem. Soc. 2010, 132, 4025–4028.
BOPhR
O
OH
gauchestrain
R
RO
B O
O
PhH
H
R
(Z)BOPh
RO
OH
R(E)
▶ Diastereoselectivity is determined by gauche strain vs A1,2-strain
R H
O
R
R Ph
OH
R
(E)
R
R
Ph
OHR
(Z) R
R
R
R
R
R H
O
R
OB
O
OB O
OB O
PhPh
PhPh
E/Z>99:1
E/Z30:70
E/Z1:>99
Small
Large
(pin)B
R(pin)B R
BOPh O
OH
Me
HBOPh O
OH
Me
H
Impact of Substituent at γ-Position
Hoffmann, R. W.; Zeiss, H. J. Angew. Chem. Int. Ed. 1979, 18, 306–307.Hoffman, R. W.; Weidmann, U. J. Organomet. Chem. 1980, 195, 137–146.
Hoffmann, R. W.; Zeiss, H. J. J. Org. Chem. 1981, 46, 1309–1314.Hoffmann, R. W. Angew. Chem. Int. Ed. 1982, 21, 555–566.
Roush, W. R.; Ando, K.; Powers, D. B.; Palkowitz, A. D.; Halterman, R. L. J. Am. Chem. Soc. 2002, 112, 6339–6348.
BOPh O
OH
Me
H
BOPh O
OH
Me
H
R
R
RR
RRH
O
R
R
R R
RR
▶ Diastereoselectivity is determined by E/Z in allylboronates
(Z)(E)(R)(R)
(R)(R)OH
PhMeR
R(S)(S)
Me(R)(R)
OH
PhR
RRH
O
R
anti syn
= Ph
R
R
= Me
R (S)(S)
OH
R (R)(R)
OH
Impact of Chiral Auxiliaries in Allylboration
Brown, H. C.; Bhat, K. S. J. Am. Chem. Soc. 1986, 108, 293–294.Stürmer, R.; Hoffmann, R. W. Synlett 1990, 1990, 759–761.
Roush, W. R.; Grover, P. T. Tetrahedron Lett. 1990, 31, 7567–7570.Barrett, A.; Malecha, J. W. J. Org. Chem. 1991, 56, 5243–5245.
Roush, W. R.; Gover, P. T.; Lin, X. Tetrahedron Lett. 1992, 48, 1981–1998.Hunt, J. A.; Roush, W. R. J. Org. Chem. 1997, 62, 1112–1124.
Roush, W. R.; Pinchuk, A. N.; Micalizio, G. C. Tetrahedron Lett. 2000, 41, 9413–9417.
+
50 : 50
B O
OB O
O
B O
OCO2
iPr
CO2iPr
94 : 6
R H
O
R
O
B O
O
R
H
R
O
O B
O
H
R
OH
Rracemic
R R
R R
(R)-isomer : (S)-isomer
(R)-isomer : (S)-isomer
1 : 99(R)-isomer : (S)-isomer▶B-chiral allylboronates: require stoichiometric amount of chiral auxiliary
▶C-chiral allylboronates: few catalytic synthetic methods are available
B-chiral
C-chiral
B O
O
Cl
Ⅰ. Introduction - Character of allylboronates - Mechanisms for diastereoselectivity
Ⅱ. Asymmetric allylboration
Ⅲ. Lewis acid catalyzed allylboration
Ⅳ. Recent researches
Allylboron Compounds with Chiral Auxiliaries
Herold, T.; Hoffmann, R. W. Angew. Chem., Int. Edit. 1978, 17, 768–769.Haruta, R.; Ishiguro, M.; Ikeda, N.; Yamamoto, H. J. Am. Chem. Soc. 1982, 104, 7667–7669.
Brown, H. C.; Jadhav, P. K. J. Am. Chem. Soc. 1983, 105, 2092–2093.Roush, W. R.; Walts, A. E.; Hoong, L. K. J. Am. Chem. Soc. 1985, 107, 8186–8190.
Garcia, J.; Kim, B. M.; Masamune, S. J. Org. Chem. 1987, 52, 4831–4832.Reetz, M. T. Pure and Applied Chemistry 1988, 60, 1607–1614.
Roush, W. R.; Banfi, L. J. Am. Chem. Soc. 1988, 110, 3979–3982.Short, R. P.; Masamune, S. J. Am. Chem. Soc. 1989, 111, 1892–1894.
Corey, E. J.; Yu, C. M.; Kim, S. S. J. Am. Chem. Soc. 1989, 111, 5495–5496.Roush, W. R.; Grover, P. T. J. Org. Chem. 1995, 60, 6641–6641.
Burgos, C. H.; Canales, E.; Matos, K.; Soderquist, J. A. J. Am. Chem. Soc. 2005, 127, 8044–8049.Canales, E.; Prasad, K. G.; Soderquist, J. A. J. Am. Chem. Soc. 2005, 127, 11572–11573.
Hoffmann, 1978 Yamamoto, 1982 Roush, 1985
Corey, 1989
Brown, 1983 Roush, 1988 Masamune, 1987
BR1
R2
O
O
PhBR1
R2
O
OCO2
iPr
CO2iPr
BR1
R2
N
NPh
Ph
Ts
Ts
BR1
R2
BR1
R2
O
O N
N
O
OBn
Bn BR1
R2 Me
Me
R1 and/or R2 = H or Me
Soderquist, 2005
BTMSR2
R1
Roush’s Allylboration
Gung, B. W.; Xue, X.; Roush, W. R. J. Am. Chem. Soc. 2002, 124, 10692–10697.Roush, W. R.; Banfi, L. J. Am. Chem. Soc. 1988, 110, 3979–3982.
B O
OCO2
iPr
CO2iPr B3LYP/6-31G*
energy difference: 1.75 (kcal/mol)
B-O+
R
OO
O O iPr
OO
iPr
Favored TS
vs ≡
Electrostatic repulsion
Stabilized by no‒p*c=o interaction
BR1
R2
O
O N
N
O
OBn
Bn
B3LYP/6-31G* energy difference: 2.14 (kcal/mol)
B
RO
HO
O CO2iPrO
OiPr
TS A'
H
OR
BO
O
iPrO2C
O
iPrO
TS B'
Improved chiral auxiliary
Ⅰ. Introduction - Character of allylboronates - Mechanisms for diastereoselectivity
Ⅱ. Asymmetric allylboration
Ⅲ. Lewis acid catalyzed allylboration
Ⅳ. Recent researches
Discovery of Lewis Acid Catalyzed Allylboration I▪First Lewis acid catalyzed allylboration
Hoffmann, R. W.; Krüger, J.; Brückner, D. New J. Chem. 2001, 102–107.Kennedy, J. W. J.; Hall, D. G. J. Am. Chem. Soc. 2002, 124, 11586–11587.
Kennedy, J. W. J.; Hall, D. G. J. Org. Chem. 2004, 69, 4412–4428.Siu Hong Yu; Ferguson, M. J.; McDonald, R.; Hall, D. G. J. Am. Chem. Soc. 2005, 127, 12808–12809.
Elford, T. G.; Arimura, Y.; Yu, S. H.; Hall, D. G. J. Org. Chem. 2007, 72, 1276–1284.Ramachandran, V. P.; Pratihar, D.; Biswas, D. Org. Lett. 2006, 8, 3877–3879.
Ramachandran, P. V.; Pratihar, D. Org. Lett. 2007, 9, 2087–2090.
MeO2CB O
O
R
(pin)BO CO2Me
H OTf
RCHO (2.0 equiv)TfOH (20 mol %)toluene, 0 ºC, 16 h
RH
MeO O
H MeHR
MeO O
H Me
O
O
R57%, >19:1 dr
R =
OMeMeO
MeO
Br
▪First Brønsted acid catalyzed allylboration
B(pin)RCHO (1.5 equiv)Sc(OTf)3 (10 mol %)toluene, rt, 24 h
Me
R = c-C6H532% yield
Bu
CO2EtO
O
BuMeR
R
OH
Bu Me
CO2Et
R = n-butyl62% yield
Discovery of Lewis Acid Catalyzed Allylboration II
▶ Improvement of reactivity and diastereoselectivity
Ishiyama, T.; Ahiko, T.-A.; Miyaura, N. J. Am. Chem. Soc. 2002, 124, 12414–12415.Lachance, H.; Lu, X.; Gravel, M.; Hall, D. G. J. Am. Chem. Soc. 2003, 125, 10160–10161.
Ramachandran, P. V.; Pratihar, D.; Biswas, D. Chem. Commun. 2005, 1988–1989.
B(pin) PhCHOLewis acidtoluene–78 ºC, 4 h
Ph
OH
MenoneAlCl3Sc(OTf)3
trace92% yield94% yieldMe
B(pin)
Me
or or
Ph
OH
Me
anti = 99%anti = 99%
noneAlCl3Sc(OTf)3
trace87% yield89% yield
syn = 98%syn = 98%
B(pin) Et2AlCl/(S)-BINOLtoluene–78 ºC, 4 h
Ph
OHMe
Me
40% yield51% ee99% anti
+PhCHO
▶ Moderate enantioselectivity
▪Impact of Lewis acid in allylboration
▪Chiral diol/Lewis acid combination catalyst
OHOH
(S)-BINOL
Mechanism of Lewis Acid Catalyzed Allylboration
R = pinacolato L.A. = AlCl3 TS energies (kcal/mol) B3LYP/6-311G
OR
O BOR
H
Ph
OR
O BOR
H
Ph
L.A.
+30.1+23.8
+6.3 +12.5OR
O BOR
H
Ph
L.A.
OR
O BOR
H
Ph
L.A.
background reaction (D)
pseudoequatorial boronate activation (A)
pseudoaxial boronate activation (B)
aldehyde activation (C)(A) (B)
(C)(D)
Omoto, K.; Fujimoto, H. J. Org. Chem. 1998, 63, 8331–8336.Rauniyar, V.; Hall, D. G. J. Am. Chem. Soc. 2004, 126, 4518–4519.
Sakata, K.; Fujimoto, H. J. Am. Chem. Soc. 2008, 130, 12519–12526.
B
PhCHO
+ Ph
OHwith and withoutSc(OTf)3
–78 ºC
▶ No rate acceleration with Sc(OTf)3
▪Calculated T.S. energies
▪Lewis acid catalyst with alkyl borane reagents
Development of Chiral Lewis Acid Catalysts I
HO OH8 8
(R,R)-Vivol
Kazuaki Ishihara; Shingo Nakamura; Masanobu Kaneeda, A.; Yamamoto, H. J. Am. Chem. Soc. 1996, 118, 12854–12855.Rauniyar, V.; Hall, D. G. Angew. Chem. Int. Ed. Engl. 2006, 45, 2426–2428.
Rauniyar, V.; Hall, D. G. Synthesis 2007, 2007, 3421–3426.Rauniyar, V.; Zhai, H.; Hall, D. G. J. Am. Chem. Soc. 2008, 130, 8481–8490.
Rauniyar, V.; Hall, D. G. J. Org. Chem. 2009, 74, 4236–4241.
B(pin)(10 mol %)
Na2CO3 (0.2 equiv)4 Å MS, toluene, –78 ºC, 12 h
R
OH
+
RCHO
OSnCl4
O HH
76–90%, up to 80% ee(R = aryl, alkyl)
B(pin) diol (5 mol %)SnCl4 (3.8 mol %)
Na2CO3 (0.1 equiv)4 Å MS, toluene, –78 ºC, 4 h
OH
+
(R,R)-Vivol(R,R)-F-Vivol
PhCHO
Ph99%, 85% ee95%, 96% ee
▶ Achievement of enantioselective allylboration
(R,R)-F-Vivol
HO OH8 8
FF
Development of Chiral Lewis Acid Catalysts II
T Robert Wu; Lixin Shen, A.; Chong, J. M. Org. Lett. 2004, 6, 2701–2704.Sha Lou; Philip N Moquist, A.; Schaus, S. E. J. Am. Chem. Soc. 2006, 128, 12660–12661.
Paton, R. S.; Goodman, J. M.; Pellegrinet, S. C. Org. Lett. 2008, 11, 37–40.Barnett, D. S.; Moquist, P. N.; Schaus, S. E. Angew. Chem. Int. Ed. Engl. 2009, 48, 8679–8682.
Jain, P.; Antilla, J. C. J. Am. Chem. Soc. 2010, 132, 11884–11886.Chen, M.; Roush, W. R. J. Am. Chem. Soc. 2012, 134, 10947–10952.
B O
OPh
OH
PhCHO (1.2 equiv)
(R)-TRIP-PA (5 mol %)toluene, 0 ºC, 16 h
MeMe
Ph
OH
Me
or
B O
O
Me
syn
anti
or
95% yield99% ee96% de
95% yield94% ee96% de
O
OP
O
OH
i-Pri-Pr
i-Pr
i-Pr
i-Pri-Pr(R)-TRIP-PA
▪Asymmetric allylation of Ketone
BO
OPh
OH
(S)-cat. (4 mol %)tBuOH, rt, 24 h
Me
Ph
OH
Me
or
96% yield98% ee94% de
94% yield94% ee96% de
BO
Oor
Ph Me
OMe
Me
(S)-cat.
OHOH
Br
Br
▪Enantio- and diastereoselective allylation
Ⅰ. Introduction - Character of allylboronates - Mechanisms for diastereoselectivity
Ⅱ. Asymmetric allylboration
Ⅲ. Lewis acid catalyzed allylboration
Ⅳ. Recent researches
Sebelius, S.; Szabo, K. J. Eur. J. Org. Chem. 2005, 2005, 2539–2547.Cmrecki, V.; Eichenauer, N. C.; Frey, W.; Pietruszka, J. Tetrahedron 2010, 66, 6550–6564.
Chen, J.; Scott, H. K.; Hesse, M. J.; Willis, C. L.; Aggarwal, V. J. Am. Chem. Soc. 2013, 135, 5316–5319.Chen, J. L. Y.; Aggarwal, V. K. Angew. Chem. Int. Ed. Engl. 2014, 53, 1–6.
Allylation with in situ Generated Borinic Esters
O
B
HPh
i-Pr
H
B(pin)
32 ppm (11B NMR)
i-Pr
n-BuLi
–78 ºC15 min
B
7 ppm (11B NMR)i-Pr
O
O
Bu
Li
B
51 ppm (11B NMR)i-Pr
BuTFAA
–78 ºC30 min
O
BOH
i-Pr
Ph
rt14 hPhCHO
Bu
OOTFA
O
O
Phi-Pr
OB O
O
21 ppm (11B NMR)
Phi-Pr
OBO
OTFA
33 ppm (11B NMR)
Bu
–78 ºC30 minPhCHO
OTFA
68% yieldE/Z = 26:7494% ee
68% yieldE/Z = >99:190% ee
92% ee
Pd-catalyzed Asymmetric Diboration
Pelz, N. F.; Woodward, A. R.; Burks, H. E.; Sieber, J. D.; Morken, J. P. J. Am. Chem. Soc. 2004, 126, 16328–16329.Angela R Woodward; Heather E Burks; Louis M Chan, A.; Morken, J. P. Org. Lett. 2005, 7, 5505–5507.
Burks, H. E.; Liu, S.; Morken, J. P. J. Am. Chem. Soc. 2007, 129, 8766–8773.Burks, H. E.; Kliman, L. T.; Morken, J. P. J. Am. Chem. Soc. 2009, 131, 9134–9135.
Ph •
Pd2(dba)3 (2.5 mol %)(R,R)-L1 (6 mol %)B2(pin)2, toluene
OP
ON
O
O
ArAr
Ar ArL1: Ar = PhL2: Ar = 3,5-Me2C6H3
Ph
B(pin)B(pin)
88% ee
PhCHO, rtthen H2O2
PhO
Ph
OH
BO
O
O
Ph
B(pin)
Ph H
(pin)B
Ph
O
O
OB
PhH
A(1,2)56%, 82% ee
vs
Pd2(dba)3 (2.5 mol %)(R,R)-L1 (6 mol %)B2(pin)2, toluene
84% ee
then H2O2
66%, 82% eeMe5
5
MeB(pin)
PhCHO
5
MeOHB(pin)
PhHO
▪α-Chiral β-boryl allylboronates
▪α-Chiral σ-boryl allylboronates
Allylation with α,α-Disubstituted Allylboronates▪Previous works
B(pin)
Me CyPh
OHCy
RCHO
94% ee, 1:1 E/Zα-dialkyl
Ph
OH
94% ee, 10:1 E/Z
B(pin)RCHO
α-alkyl, β-methyl
B(pin)OMe
Ph
PhMe
H
Me
Favor TS (2.3 kcal/mol)
O
B(pin)Me
HPh
Me
Me
Disfavor TS rCH-Ar 3.4 Å
▶ Difficult to control E/Z selectivity
Guzman-Martinez, A.; Hoveyda, A. H. J. Am. Chem. Soc. 2010, 132, 10634–10637.Chen, J.; Scott, H. K.; Hesse, M. J.; Willis, C. L.; Aggarwal, V. J. Am. Chem. Soc. 2013.
Hesse, M. J.; Essafi, S.; Watson, C. G.; Harvey, J. N.; Hirst, D.; Willis, C. L.; Aggarwal, V. K. Angew. Chem. Int. Ed. 2014, 53, 1–6.
JACS, 2010 JACS, 2013
▪Enantio- and diastereoselective addition to aldehyde i) s-BuLi, Et2O –78 ºC, 15 minii)
B(pin)
RCHO, THF–78 ºC to rt, 16 h R
OH
99%, >99:1 dr, >99:1 er99%, >99:1 dr, 99:1 er
Ph
OCb
B(pin)
–78 ºC, 1 h
iii) reflux, 16 h
PhPh
R = PhR = Cy
Hydroboration-Aldehyde Allylboration Sequence
Brown, H. C.; Narla, G. J. Org. Chem. 1995, 60, 4686–4687.Barrett, A. G. M.; Braddock, D. C.; Koning, P. D.; White, A. J. P.; Williams, D. J. J. Org. Chem. 1999, 65, 375–380.
Flamme, E. M.; Roush, W. R. J. Am. Chem. Soc. 2002, 124, 13644–13645.Peng, F.; Hall, D. G. J. Am. Chem. Soc. 2007, 129, 3070–3071.
Chen, M.; Handa, M.; Roush, W. R. J. Am. Chem. Soc. 2009, 131, 14602–14603.Chen, M.; Ess, D. H.; Roush, W. R. J. Am. Chem. Soc. 2010, 132, 7881–7883.
Chen, M.; Roush, W. R. J. Am. Chem. Soc. 2011, 133, 5744–5747.Chen, M.; Roush, W. R. J. Am. Chem. Soc. 2013, 135, 9512–9517.
•R'2B
R1 R2
OH OH
R1
R2OH
OH
OB
O
OB O
PhPh
PhPh
65–87% 89–96% ee >20:1 dr
72–95% 91–95% ee >14:1 dr
-B(OR)2 =
R1CHO
R2CHOor
(dIpc)2BH
i) R1CHO ii) H2O2, NaOH
60–75% 90–95% ee >20:1 dr
R1
OH
OH
BR'2B
▪Allene hydroboration/aldehyde allylboration reaction sequences
γ-Alkoxyallylboronates
Hoffmann, R. W.; Kempher, B. Tetrahedron Lett. 1981, 22, 5263–5266.Wuts, P. G.; Bigelow, S. S. J. Org. Chem. 1982, 47, 2498–2500.
Brown, H. C.; Jadhav, P. K.; Bhat, K. S. J. Am. Chem. Soc. 1988, 110, 1535–1538.Moriya, T.; Suzuki, A.; Miyaura, N. Tetrahedron Lett. 1995, 36.
Ganesh, P.; Nicholas, K. M. J. Org. Chem. 1997, 62, 1737–1747.Yamamoto, Y.; Miyairi, T.; Ohmura, T.; Miyaura, N. J. Org. Chem. 1998, 64, 296–298.
Yamamoto, Y.; Kurihara, K.; Yamada, A.; Takahashi, M. Tetrahedron 2003, 59.Muñoz-Hernández, L.; Soderquist, J. A. Org. Lett. 2009, 11, 2571–2574.
B
MeO
Brown et al. (1988)
BTBSO O
OCO2
iPr
CO2iPr
Miyaura et al. (1998)
BTMS
OMe
Soderquist et al. (2009)
BMeO O
O
Hoffmann et al. (1981)Wuts et al. (1982)
O
B(pin)
R
Hall et al. (Cr and Pd cat.)R = OEt (2003), H (2009)
BnO
B(pin)
RMeO
B(pin)
Ito et al. (2014) (Cu cat.)
Deligny, M.; Carreaux, F.; Carboni, B.; Toupet, L. Chem. Commun. 2003, 276–277.Gao, X.; Hall, D. G. J. Am. Chem. Soc. 2003, 125, 9308–9309.
Possémé, F.; Deligny, M.; Carreaux, F.; Carboni, B. J. Org. Chem. 2007, 72, 984–989.Lessard, S.; Peng, F.; Hall, D. G. J. Am. Chem. Soc. 2009, 131, 9612–9613.
Penner, M.; Rauniyar, V.; Kaspar, L. T.; Hall, D. G. J. Am. Chem. Soc. 2009, 131, 14216–14217.Ding, J.; Hall, D. G. Angew. Chem. Int. Ed. 2013, 52, 1–6.
Yamamoto, E.; Ozaki, T.; Miya, T.; Ito, H. J. Am. Chem. Soc. 2014, 136, 16515–16521.
Allylation with α-Chiral γ-Alkoxyallylboronates
▪Asymmetric syntheses of heterocyclic γ-alkoxyallylboronates
▪Asymmetric synthesis of linear γ-alkoxyallylboronates
R'
ORRO R' OR
B(pin)CuCl/(R,R)-BenzP* R''CHO
R'
ORR''
OHZnBr2
68–82% yield, E/Z = 85:15–98:2anti/syn >95:5, 94–98% ee
62–94%, 91–98% ee
(pin)B–B(pin)K(O-t-Bu)
O B(pin)R
N
OCr
Oada
Cl
cat., MS 4 Å
O
B(pin)
R
PhCHO OPh
HOH
R
cat.O OTf
Pd(OAc)2TANIAPHOSBase R = OEt: >98% de, 96% ee
R = H: >96% de, 93% ee
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