Indoles dimethyl diazomalonate

Indoles treated with dimethyl diazomalonate under catalysis by rhodium(II) acetate undergo GH and NH insertion reactions depending on the substitution pattern on the indole moiety (e.g., Scheme 84) <2002JOC6247>. 

Cyclopropanation of aromatic and heteroaromatic compounds with dimethyl diazomalonate in the presence of Rh2(OAc)4 is usually accompanied by dissociation of one of the cyclopropane bonds. In reaction of )V-protected indoles this led to a very efficient introduction of the malonate substituent at position 3 (eq 21). When the 3-position was substituted, the malonate moiety was installed into the 2-position, however, yields were significantly diminished. Remarkably, no cyclopropanation of the a-olefin at the side chain was observed (eq 22) Although the reactions featured here represent a formal insertion of the carbenoid species... 

Cu(acac)2] was also reported to effectively catalyze the carbenoid C-H insertion of various indoles with dimethyl diazomalonate in refluxing benzene. The regioselectivity of the alkylation depends on the substituent pattern of the indole. Interestingly, while N-H free indole was used as substrate in the reaction, C3-aikylation product was obtained in good yield and only trace amount of N-H insertion product was detected (eq 56). 

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