Synthesis and Stereochemistry of 3, 7-Diazatricyclo[4.2.2.2^{2, 5}]dodeca-9, 11-dienes Derived by [4+4] Cyclodimerization of 2, 3-Dihydroisoquinoline Derivatives

Abstract

2-Acyl(or sulfonyl)-c-4-bromo-γ-1-cyano-t-3-methoxy-1, 2, 3, 4-tetrahydroisoquinolines 2b-g when treated with triethylamine or K₂CO₃ gave cyclodimers 5b-g of 2-acyl(or sulfonyl)-1-cyano-3-methoxy-2, 3-dihydroisoquinolines in high yields. The dimers are composed of two tetrahydroisoquinoline units fused at the 1, 1'- and 4, 4'-positions to form a triheterocyclic 3, 7-diazatricyclo[4.2.2.2^{2, 5}]dodeca-9, 11-diene ring. 2, 3-Dihydroisoquinoline type compounds 3 are the key intermediate for this unusual [4+4] cyclodimerization. The structures of the dimers with an exo-type configuration have been determined by X-ray crystallography. The reaction mechanism of the cyclodimerization is discussed in conjunction with the stereochemistry of the products.