Vilsmeier Reaction Of α,α-dicyanoolefins: Synthesis Of Multi-substituted Pyridines

Multi-substituted pyridines occupies an important position in organic chemistry.According to recent decades,multi-substituded pyridines with specific group were potential as optical and electronic material.Multi-substitute pyridines were also found in lots of medicines and pesticides.Since Chichibabin synthesized unsubstituted pyridines in 1924,people have never stopped exploring pyridines.The synthesis of multi-substituted pyridines have always been an important topic.At present,the methods for synthesizing multi-substituted alkyl and arylpyridines have gradually matured,but obtaining functionalized multi-substituted pyridines are still an urgent problem.Usually,there are two strategies:（1）Introducing substituents on the pyridine ring;（2）Constructing pyridine structures through cycloaddition of non-cyclic compounds.The former often has certain limitations,while the latter has become a hotly discussed topic.In this paper,a novel Vilsmeier reagent composed of triphosgene and DMF was used to convertα,α-dicyanoalkenes into 2-chloro-5-formyl-3-cyanopyridines in one pot,the operation steps are simplified,and compared to the POCl₃ used in classical Vilsmeier reagents,triphosgene has advantages such as low spoilage,low toxicity,less harm to experimenters,and easy storage.In substrate expansion,we obtained a series of tetrasubstituted 2-chloro-5-formyl-5-formyl-3-cyanopyridines with shorter reaction time,mild conditions and considerable yields.It provides a new idea for the synthesis of multi-substituted pyridines compounds.