Page 860 - Advanced Organic Chemistry Part B - Reactions & Synthesis

836 9.3.2. Carbon-Carbon Bond-Forming Reactions

CHAPTER 9 As with the silanes, the most useful synthetic procedures involve electrophilic
Carbon-Carbon attack on alkenyl and allylic stannanes. The stannanes are considerably more reactive
Bond-Forming Reactions than the corresponding silanes because there is more anionic character on carbon in the
of Compounds of Boron,
Silicon, and Tin C–Sn bond and it is a weaker bond. 156 The most useful reactions in terms of syntheses
involve the Lewis acid–catalyzed addition of allylic stannanes to aldehydes. 157 The
reaction occurs with allylic transposition.

R 3
3
RCH O + R CH CHCHSnBu 3 RCHCHCH CHR 1
R 1 HO

There are also useful synthetic procedures in which organotin compounds act
as carbanion donors in transition metal–catalyzed reactions, as discussed in
Section 8.2.3.3. Organotin compounds are also very important in free radical reactions,
as is discussed in Chapter 10.

9.3.2.1. Reactions of Allylic Trialkylstannnanes. Allylic organotin compounds are not
sufficiently reactive to add directly to aldehydes or ketones, although reactions with
aldehydes do occur with heating.

100°C
Cl CH O + CH 2 CHCH Sn(C H ) Cl CHCH 2 CH CH 2
2
2 5 3
4 h
OSn(C H )
2 5 3
90%
Ref. 158
Use of Lewis acid catalysts allows allylic stannanes to react under mild conditions.
As is the case with allylic silanes, a double-bond transposition occurs in conjunction
with destannylation. 159

CH 3 CH 2 Sn(C H ) BF CH 3
4 9 3
PhCH O + 3 PhCHCHCH CH 2
H H
OH 92%

The stereoselectivity of addition to aldehydes has been of considerable interest. 160
With benzaldehyde the addition of 2-butenylstannanes catalyzed by BF gives the syn
3
isomer, irrespective of the stereochemistry of the butenyl group. 161

156 J. Burfeindt, M. Patz, M. Mueller, and H. Mayr, J. Am. Chem. Soc., 120, 3629 (1998).
157
B. W. Gung, Org. React., 64, 1 (2004).
158
K. König and W. P. Neumann, Tetrahedron Lett., 495 (1967).
159 H. Yatagai, Y. Yamamoto, and K. Maruyama, J. Am. Chem. Soc., 102, 4548 (1980); Y. Yamamoto,
H. Yatagai, Y. Naruta, and K. Maruyama, J. Am. Chem. Soc., 102, 7107 (1989).
160 Y. Yamomoto, Acc. Chem. Res., 20, 243 (1987); Y. Yamoto and N. Asao, Chem. Rev., 93, 2207 (1993).
161
(a) Y. Yamamoto, H. Yatagai, H. Ishihara, and K. Maruyama, Tetrahedron, 40, 2239 (1984);
(b) G. E. Keck, K. A. Savin, E. N. K. Cressman, and D. E. Abbott, J. Org. Chem., 59, 7889 (1994).