Efficient cyclotrimerization of bicyclic vic-bromostannylalkenes promoted by copper(I) thiophen-2-carboxylate.
Copper(I) thiophen-2-carboxylate was successfully employed in the trimerization of [2.2.1] bicyclic vic-bromotrimethyltin olefins (in their racemic composition), bearing different functionalities, to invariably obtain almost quantitative yields of the syn and anti tris-annelated benzenes. The two isomers come in different ratios, smaller than or equal to the statistical 1:3 ratio, depending on the steric hindrance opposed by the functionalities. In the case of enantiopure (3-bromo-4,7,7-trimethylbicyclo[2.2.1]hept-2-en-2-yl)trimethylstannane, the 1:9 ratio found with Cu(NO(3))(2).3H(2)O increases to 1:6.
Borsato
Giuseppe
G
Dipartimento di Scienze Ambientali and Dipartimento di Chimica, Università Ca' Foscari di Venezia, Dorsoduro 2137, Italy.
De Lucchi
Ottorino
O
Fabris
Fabrizio
F
Groppo
Luca
L
Lucchini
Vittorio
V
Zambon
Alfonso
A