Remarkable Substituent Effects on the Chemoselectivity of Rhodium(II) Carbenoids Derived from N-(2-Diazo-3-oxobutyryl)-L-phenylalanine Esters

Article abstract of DOI:10.1016/0040-4020(95)00464-J

Four different N-(alkyl/aryl)-N-(2-diazo-3-oxobutyryl)-L-phenylalanine methyl esters 1b-e have been synthesized and subjected to rhodium(II) acetate catalyzed diazodecomposition.Thereby a strong dependence of the product distribution from the type of nitrogen bound substituent was observed.The bis(4-chlorophenyl)methyl derivative 1b provided similar products in comparable yields as the benzhydryl derivative 1a.The N- diazoamide 1c gave exclusively the cycloheptapyrrole 4c, whereas the N-fluorenyl derivative 1d yielded, upon treatment with Rh2(OAc)4, mainly the spirolactam 5d.The N-(4-nitrophenyl) diazoamide 1e gave, under the same conditions, the nitroindole 7.