Migratory insertion of isocyanide into a ketenyl–tungsten bond as key step in cyclization reactions

Abstract

The prototype ketenyl ligand is bound end-on despite a formal 16 valence electron count at the metal. This situation opens a reaction pathway for a multicomponent cyclization centred on the migration of the ketenyl ligand.

Construction of Tetrazole Derivatives via Sequential Ugi‐N3/Pd‐Catalyzed Isocyanide Insertion Reactions

“…Subsequent reactions with different types of metal catalysts such as CoBr 2 , PdCl 2 , Pd(OTf) 2 , Pd 2 (dba) 3 , and Pd(OAc) 2 demonstrated that Pd(OAc) 2 is more suitable for the conversion with a maximum yield of 35 % (Table 1, entries 2-6). The base screening result indicated that Cs 2 CO 3 appeared to be the best base, and the outcome was observably increased to 74 % (Table 1, entries 7- 11). By switching the solvents from 1,4-dioxane, CH 3 CN, THF, and DMF to PhCl (Table 1, entries 12-16), none of the solvents resulted in a positive yield.…”

“…Among them, the isocyanide-based Ugi-N 3 reactions [9] have been widely reported for the synthesis of skeleton models containing tetrazole structures with suitable biological activities. In the past decades, the isocyanide compounds have been regarded as valuable starting materials for the exploitation of abundant reactions such as MCRs, [10] one-pot tandam/cyclization reactions, [11] insertion reactions, [12] and others [13] based on the carbene-like reactivity of carbon atom. Especially, the transition-metal-catalyzed isocyanide insertion reactions have exhibited significant applications in heterocyclic synthesis due to their excellent atomic and step economy.…”