Synthesis and chemical behaviors of 12-substituted dibenz[c,f][1,5]azastibocine and dibenz[c,f][1,5]azabismocine derivatives: evidences of 10-Pn-4 type hypervalent interaction

A series of 12-substituted 6-methyl-5,6,7,12-tetrahydro-12-X-dibenz[c,f][1,5]azastibocine (1) and azabismocine (2) were prepared. Both 1 H and 13 C NMR signals of the N-methyl group were shifted to downfield by electron-withdrawing substituent at the pnictogen atoms and the shift was linearly correlated with Hammett σ m values.