Abstract
N-Alkyl α-diazo-γ-butyrolactams, previously found to be unstable and to undergo unproductive dimerization to bishydrazones, were successfully converted immediately to various X–H insertion products with alcohols, aromatic amines and thiols via an in situ RhII-catalyzed reaction. With aliphatic amines or unreactive, sterically hindered anilines, the reactions tended to yield enamine adducts.
Highlights
We described the first synthesis and subsequent transformations of a rare type of cyclic α-diazocarbonyl compounds, namely, α-diazo-γ-butyrolactams [1]
N-arylα-diazo-γ-butyrolactams 1 were efficiently transformed into pyrrolinones 2 upon the treatment with AgOTf (1 mol %) and into α-alkoxy derivatives 3 via Rh2(OAc)4-catalyzed O–H insertion reactions with various alcohols
The instability of N-alkyl-α-diazo-γ-butyrolactams 4 compared to the N-aryl counterparts 1, was most likely related to the reduced electronwithdrawing character of the lactam carbonyl group in the former compared to the latter. This assumption is further supported by the fact that ortho-substituted N-aryl derivatives 1 are as unstable as the N-alkyl derivatives 4 [1]. Faced with this serious limitation of the reactivity scope, we set off to investigate the possibility of using unstable compounds 4 in situ, promptly after their formation, in various RhII-catalyzed X–H insertion reactions, the recently described rhodium carbene insertion into O–H [1], N–H [2] and S–H [3] bonds of alcohols, aromatic amines, and thiols, respectively
Summary
We described the first synthesis and subsequent transformations of a rare type of cyclic α-diazocarbonyl compounds, namely, α-diazo-γ-butyrolactams [1]. N-arylα-diazo-γ-butyrolactams 1 were efficiently transformed into pyrrolinones 2 upon the treatment with AgOTf (1 mol %) and into α-alkoxy derivatives 3 via Rh2(OAc)4-catalyzed O–H insertion reactions with various alcohols.
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