The monosubstituted thio-imidazolones, where the methylene hydrogen has been replaced, yielded in every case thio-ethers.The hydrolysis of certain of these imidazolones has been studied.

A vinylcarbenoid approach toward N-functionalization of NH-pyrazoles is presented. The rhodium(II)-catalyzed reaction of methyl styryl-diazoacetate (1) or dimethyl 2-diazoglutaconate (3) with 3,5-disubstituted pyrazoles gave products of carbenoid N-H insertion in high combined yields, although regioselectivity issues posed by the pyrazole or the vinylcarbenoid moiety as well as positional and configurational isomerism concerning the C,C double bond of the latter led to product mixtures. The ambident reactivity of the vinylcarbenoid derived from 1 could be steered by the catalyst: while Rh 2 (OAc) 4 yielded products of direct carbenoid insertion preferentially, silver(I) catalysis strongly favored reaction at the vinylogous site of the carbenoid resulting in an N-allylation of the pyrazoles.

The rhodium‐catalyzed reactions of methyl styryl‐diazoacetate or dimethyl 2‐diazoglutaconate with the title pyrazoles lead to product mixtures as a result of the regioselectivity issues of the pyrazole or the vinylcarbenoid moiety as well as positional and configurational isomerism due to the C=C double bond of the latter.

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