Page 859 - Advanced Organic Chemistry Part B - Reactions & Synthesis

H Li H Sn(CH ) 835
3 3
+ (CH ) SnCl
3 3
Ph Ph OCH 3 SECTION 9.3
OCH 3
Ref. 149
Organotin Compounds
There are several procedures for synthesis of terminal alkenyl stannanes that
involve addition to aldehydes. A well-established three-step sequence culminates in a
radical addition to a terminal alkyne. 150

P(Ph) 3 1) n-BuLi (n-C 4 9 3
H ) SnH
RCH O + CBr 4 RCH CBr 2 RC CH RCH CHSn(n-C 4 H 9 ) 3
Zn 2) H O AlBN
2
Another sequence involves a dibromomethyl(trialkyl)stannane as the starting material.
On reaction with CrCl , addition to the aldehyde is followed by reductive elimi-
2
nation. 151
CrCl 2
RCH O + R′ SnCHBr 2 RCH CHSnR′ 3
3
LiI
Deprotonated trialkylstannanes are potent nucleophiles. Addition to carbonyl
groups or iminium intermediates provides routes to -alkoxy- and -amino-
alkylstannanes.

O – OR′
R′X
H )
RCH O + (C H ) SnLi RCHSn(C 4 9 3 RCHSn(C H ) Ref. 152
4 9 3
4 9 3
R NCH SPh + (C H ) SnLi R NCH Sn(C H ) Ref. 153
2
2
4 9 3
4 9 3
2
2
-Silyoxystannanes can be prepared directly from aldehydes and tri-n-butyl
(trimethylsilyl)stannane. 154
OSi(CH )
3 3
+
R′ 4 N CN –
RCH O + (n-C 4 9 3 3 3 RCHSn(n-C H )
H ) SnSi(CH )
4 9 3
Addition of tri-n-butylstannyllithium to aldehydes followed by iodination and dehydro-
halogenation gives primarily E-alkenylstannanes. 155
I R H
Ph P-I DBU
H ) SnLi
RCH CH O + (n-C 4 9 3 3 2 RCH CHSn(n-C H )
2
4 9 3
2
H Sn(n-C 4 9 3
H )
149 J. A. Soderquist and G. J.-H. Hsu, Organometallics, 1, 830 (1982).
150 E. J. Corey and P. L. Fuchs, Tetrahedron Lett., 3769 (1972).
151
M. D. Cliff and S. G. Payne, Tetrahedron Lett., 36, 763 (1995); D. M. Hodgson, Tetrahedron Lett., 33,
5603 (1992); D. M. Hodgson, L. T. Boulton, and G. N. Maw, Tetrahedron Lett., 35, 2231 (1994).
152
W. C. Still, J. Am. Chem. Soc., 100, 1481 (1978).
153 D. J. Peterson, J. Am. Chem. Soc., 93, 4027 (1971).
154 R. M. Bhatt, J. Ye, and J. R. Falck, Tetrahedron Lett., 35, 4081 (1994).
155
J. M. Chong and S. B. Park, J. Org. Chem., 58, 523 (1993).