REGIOSELECTIVE AND STEREOSELECTIVE SYNTHESIS OF (E)-2-METHYL-1-ALKENYLTRIMETHYLSTANNANES FROM 1-ALKYNES

Several procedures, which are based on the zirconium-catalyzed methyla lumination of 1-alkynes (5), have been tested for the regio- and stere oselective synthesis of (E)-2-methyl-1-alkenyltrimethylstannanes (4). The best one among these procedures as regards simplicity and mildness is that based on the water-accelerated methylalumination of compounds 5, followed by treatment with a THF solution of Me(3)SnCl. This proce dure allows the preparation of (E)-2-aryl-2-methylethenyltrimethylstan nes, (E)-2-benzyl-2-methylethenyltrimethylstannanes and (1-cycloalkeny l)-2-methylethenyltrimethylstannanes in quite high yields. On the othe r hand, (E)-2-alkyl-2-methylethenyltrimethylstannanes having high regi o- and stereoisomeric purities have been effectively and conveniently synthetized by a reaction sequence involving the zirconium-catalyzed m ethylalumination of compounds 5 according to a standard protocol and t he conversion of the alkenyldimethylalanes (7) so obtained into the co rresponding methylalanates (10), followed by treatment with a THF solu tion of Me(3)SnCl.