The BF3 and B(C6F5)(3)-catalyzed 1,3-isomerization of allylic stannanes

A spectroscopic and chemical study of the stereospecific B(C6F5)(3)-catalyz ed 1,3-isomerization of (E,S)-1-methoxymethoxy-2-butenyl tributylstannane t o (Z,S)-1-methyl-3-methoxymethoxy-2-propenyl tributylstannane is described. A pathway involving an intermediate B(C6F5)(3) adduct is proposed based up on H-1- and Sn-119-NMR data. Analogous spectral evidence was not observed i n the seemingly related BF3. OEt2-catalyzed isomerization. However, the sim ilar product ratios obtained in B(C6F5)(3) and BF3. OEt2-promoted additions of the latter stannane to o- and p-methoxybenzaldehyde reveals a close sim ilarity between the two and prompts speculation that the BF3. OEt2-catalyze d 1,3-isomerization proceeds by an analogous pathway. A pathway for the B(C 6F5)(3)-promoted addition of allylic stannanes to o-methoxybenzaldehyde is also presented. (C) 2001 Elsevier Science B.V. All rights reserved.