Azavinyl carbenes

The Rh-catalyzed annulation of triazoles has been explored by several investigators as a novel indole synthesis. Fokin s team generated azavinyl carbenes with rhodium and parlayed this reaction into an indole synthesis (equation 3) [54], Davies and colleagues described a one-pot indole synthesis from tosyl azide and cyclohexenyl derivatives involving an in situ triazole formation (equation 4) [55], and Lin reported a synthesis of 3-indolylimines using a similar approach (equation 5) [56]. Miura and coworkers effected the Rh-cat-alyzed intramolecular synthesis of 3,4-fused indoles... 

Another example of the exquisite reactivity of rhodium(II) azavinyl carbenes is illustrated by their addition to olefins, which is a very facile process and proceeds... 

Trisubstituted 4-oxazolines 155 were efficiently prepared from 1-sulfonyl-l,2,3-triazoles 154 and aldehydes in the presence ofRh(II) catalysts, likely through Rh(II)-azavinyl carbenes I and ylides II as reaction intermediates (13AGE1507). 

The Rh(ll) azavinyl carbenes generated by metal-catalysed decomposition of 1 -sulfonyl-1,2,3-triazoles have been shown to undergo various rearrangements, depending on the substituent a to the carbene (Scheme 10). In the case of a hydroxyl substituent (a). 

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