Isocyanides Mediated Cyclization And Arylation Of Benzo[d]oxazoles

Isocyanide is highly active in reactions since isocyano group has nucleophilicity and electrophilicity. This unique feature of isocyano group makes it particularly useful in the synthesis of nitrogen-containing heterocycles, such as pyrroles, quinolones, indoles, isquinolines as well as phenanthridines.Phenanthridines are common structural units present in natural products and biological active molecular structures. TheBPO-promoted α-phenanthridinylation of ethers by isocyanides was developed. This procedure involved dual C-C bond formation via sp2 and sp3 C-H bonds cleavage. The advantages of this method are the mild reaction conditions without transition-metal catalysts,which developed a simple method for sp3 C-H bondactivation.We next developed TBHP-promoted synthesis of 6-silyl phenanthridines with 2-isocyanobiaryls and silanes. This procedure involved C-H and Si-H bonds cleavage and C-C and C-Si bonds formation through a radical pathway. This work provided a simple and efficient method for C-Si bond formation.The frameworks of 2-arylbenzooxazole are widely found in pharmaceuticals, organic dyes and natural products. In this paper, Potassium carbonate-promoted formal arylation of benzo[d]oxazoles with acyl chloride was achieved. This reaction was triggered by the N-acylation of oxazole to form an iminium intermediate. Then, the addition of H2 O to the iminium formed the hemiacetal intermediate. After the sequential ring-opening, extrusion of CO, the ring closure and dehydration delivered the formal arylation products.