Several procedures, which are based on the zirconium-catalyzed methylalumination of 1-alkynes (5), have been tested for the regio- and stereoselective 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 procedure allows the preparation of (E)-2-aryl-2-methylethenyltrimethylstannes, (E)-2-benzyl-2-methylethenyltrimethylstannanes and (E)-2-(1-cycloalkenyl)-2-methylethenyltrimethylstannanes in quite high yields. On the other hand, (E)-2-alkyl-2-methylethenyltrimethylstannanes having high regio- and stereoisomeric purities have been effectively and conveniently synthetized by a reaction sequence involving the zirconium-catalyzed methylalumination of compounds 5 according to a standard protocol and the conversion of the alkenyldimethylalanes (7) so obtained into the corresponding methylalanates (10), followed by treatment with a THF solution of Me(3)SnCl.
REGIOSELECTIVE AND STEREOSELECTIVE SYNTHESIS OF (E)-2-METHYL-1-ALKENYLTRIMETHYLSTANNANES FROM 1-ALKYNES
BELLINA, FABIO;CARPITA, ADRIANO;
1994-01-01
Abstract
Several procedures, which are based on the zirconium-catalyzed methylalumination of 1-alkynes (5), have been tested for the regio- and stereoselective 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 procedure allows the preparation of (E)-2-aryl-2-methylethenyltrimethylstannes, (E)-2-benzyl-2-methylethenyltrimethylstannanes and (E)-2-(1-cycloalkenyl)-2-methylethenyltrimethylstannanes in quite high yields. On the other hand, (E)-2-alkyl-2-methylethenyltrimethylstannanes having high regio- and stereoisomeric purities have been effectively and conveniently synthetized by a reaction sequence involving the zirconium-catalyzed methylalumination of compounds 5 according to a standard protocol and the conversion of the alkenyldimethylalanes (7) so obtained into the corresponding methylalanates (10), followed by treatment with a THF solution of Me(3)SnCl.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
