Page 863 - Advanced Organic Chemistry Part B - Reactions & Synthesis

O OH 839
PhCH CH CCH + (CH 2 CHCH ) SnBr 2 PhCH 2 CH CCH CH CH 2 SECTION 9.3
2
3
2
2
2
2 2
CH 3 Organotin Compounds
OX
(n-C H ) SnCl 2
4 9 2
RCH O + CH 2 CHCH Sn(n-C H ) RCHCH CH CH 2
2
2
4 9 3
RCOCl or
(CH ) SiCl X = RCO or (CH ) Si
3 3
3 3
Ref. 168
The halostannanes can also be generated in situ by reactions of allylic halides with tin
metal or stannous halides.
OH
Sn H 2 O
2
PhCH O + CH 2 CHCH I PhCHCH CH CH 2
2
Ref. 169
OH
SnF 2
PhCH CHCH O + CH 2 CHCH I PhCH CHCHCH CH CH 2
2
2
Ref. 169

The allylation reaction can be adapted to the synthesis of terminal dienes by using
1-bromo-3-iodopropene and stannous chloride. The elimination step is a reductive
elimination of the type discussed in Section 5.8. Excess stannous chloride acts as the
reducing agent.

Br
SnCl 2
PhCH O + ICH CH CHBr PhCHCHCH CH 2 PhCH CHCH CH 2
2
OH

Ref. 170

Allylic Sn(II) species are believed to be involved in reactions of allylic trialkyl
stannanes in the presence of SnCl . These reactions are particularly effective in acetoni-
2
trile, which appears to promote the exchange reaction. Ketones as well as aldehydes
are reactive under these conditions. 171

168
T. Mukaiyama and T. Harada, Chem. Lett., 1527 (1981).
169
T. Mukaiyama, T. Harada, and S. Shoda, Chem. Lett., 1507 (1980).
170 J. Auge, Tetrahedron Lett., 26, 753 (1985).
171
(a) M. Yasuda, Y. Sugawa, A. Yamamoto, I. Shibata, and A. Baba, Tetrahedron Lett., 37, 5951
(1996); (b) M. Yasuda, K. Hirata, M. Nishino, A. Yamamoto, and A. Baba, J. Am. Chem. Soc., 124,
13442 (2002).