ALLYLSTANNATION. I. STEREOCHEMISTRY OF THE ADDITION OF trans/cis-2-BUTENYL-CHLORO-DI-n-BUTYLTIN TO ALDEHYDES

Article abstract of DOI:10.1016/S0022-328X(00)87430-6

2-Butenyl-chloro-di-n-butyltin, in various trans/cis ratios, reacts readily with neat RCHO (R = CH3, C2H5, C2H5(CH3)CH, (CH3)2CH, C6H5) at 25 deg C to give mixtures of threo/erythro-α-methylallylcarbinols in high yields.The same mixtures are obtained from the equilibrated mixtures obtained by redistribution between Bu3SnC4H7 (C4H7 = trans-, cis-crotyl and α-methylallyl group) and Bu2SnCl2.The reactions are characterized by a high degree of stereoselectivity, especially when bulky R groups are present.The complete allylic rearrangement and the stereoselectivity indicate that an exacyclic transition state is involved.Two stereochemically different transition states lead to two diastereoisomers, threo- and erythro-α-methylallylcarbinol in the enantioforms RS, SR and RR, SS, respectively.