Nitrile imines electrocyclization reactions

Thus in the N-silyl substituted series, 17 and 18, which rearrange thermally to the corresponding diazo compounds, the stability increases through the series R=Me, Ph, i-Pr. As discussed below, these compound undergo the usual cycloaddition and electrocyclization reactions of nitrile imines and are not simply overstabilized curiosities. The usefulness in synthesis of those with P—C bonds is probably limited since these bonds are not easily broken, but products derived from those with C—Si and C—B bonds (e.g., 21 and 22) should be capable of further... 

Reaction of dichorobenzaldoxazine with sodium azide followed by 1-propa-nethiol-triethylamine gave the tetrazine imide 367 as the major product. Its formation is thought to involve the reaction sequence shown which includes an unprecedented electrocyclization of the nitrile imine 366 as the final step (210). 

The oxidation of hydrazones 143 provides, in principle, a very convenient route to nitrile imines from easily accessible starting materials. However, the earliest reagent used, lead tetraacetate, was of limited effectiveness as yields were low and the reaction often gave high yields of diacylhydrazides as byproducts. Work has been done on the application of several other oxidants to this process to produce a more effective general route. The one that has proved most popular is chloramine T (A-chloro-iV-sodio-p-toluenesulfonamide, CAT) which is used under mild conditions and has been shown to work well for both cycloaddition (79) (e.g., in the preparation of 146 from 145) and electrocyclization (80) reactions. 

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