Vinylnitrosonium cation

The second method related to nitrosoalkene cycloaddition is the reaction of vinylnitrosonium cations with alkenes. Several intramolecular cycloaddition reactions of this type have been described <87JOC877> one example is illustrated in Scheme 15. 

The in situ generation of TV-vinyl-AT-cyclohexylnitrosonium cations from the corresponding a-chloro nitrone, e.g., AT-(2-chloroethylidene)cy-clohexylamine N-oxide (25), and their subsequent [4+ + 2] cycloaddition with electron-rich, neutral, or selected electron-deficient dienophiles have been extensively investigated (Scheme 9-1X).173-175 The intermediate im-inium salts which are derived from the regio- and stereoselective [4+ + 2] cycloadditions are not generally isolated but are subjected to the useful transformations illustrated in Scheme 9-IX. The intramolecular [4+ + 2] cycloadditions of vinylnitrosonium cations and nitroalkenes have been detailed.176... 

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