Fig. 4 |. Examples of new reductive coupling reactions.
a | Isocyanide insertion into metaiiacydopentenes can result in imido extrusion and formal [4+1] coupling with Ti, while intermediate products can be isolated with the heavier Hf congener. b | Nitrile reductive couplings lead to diazatitanacyclopentadienes that can undergo further reaction to make new π-conjugated materials. c | A general mechanistic scheme for early-transition-metal-catalysed cyclotrimerization catalysis (left) and new advances in selective heterocyclization catalysed by simple reduced Nb complexes. DCE, 1,2- dichloroethane; DME, 1,2-dimethoxyethane; equiv., equivalents; THF, tetrahydrofuran; TM, transition metal; TMS, trimethylsilyl
