Ring expansions of alkynyl cyclopentanols with iodine and Koser's reagent.
作者:Pakorn Bovonsombat、Edward McNelis
DOI:10.1016/s0040-4020(01)80339-2
日期:——
Equimolar amounts of iodine, Koser's reagent, and 1-bromoethynylcyclopentanols with none, one or two methyl groups in the alpha-position lead to ring expansions in acetonitrile at room temperature in yields of 75 to 85%. In the so-formed 2-[bromoiodomethylidene]cyclohexanones the (Z) isomer was preferred exclusively in the unsubstituted compound. The Z/E ratio was 7.7 for the dimethyl compound and 3.3 for the monomethyl case. The corresponding bromine and Koser's reagent with 1-iodoethynylcyclopentanol afforded a ring expanded product with Z/E ratio of 12:1.