Journal of the American Chemical Society 2004-07-14

Rearrangements concerted with fragmentation of cyclopropylmethoxychlorocarbene and cyclobutoxychlorocarbene in hydrocarbon solvents and Ar matrices.

Robert A Moss, Ronald R Sauers, Fengmei Zheng, Xiaolin Fu, Thomas Bally, Alexander Maltsev

Index: J. Am. Chem. Soc. 126(27) , 8466-76, (2004)

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Abstract

Fragmentations of cyclopropylmethoxychlorocarbene (6) and cyclobutoxychlorocarbene (10) lead to rearrangments that afford mixtures of cyclopropylmethyl chloride (7), cyclobutyl chloride (8), and 3-butenyl chloride (9). Isotopic substitution studies show that these rearrangments are accompanied by partial exchange of the methylene groups within 6 and 10. Surprisingly, these processes that are typical of carbocations persist in hydrocarbon solvents such as pentane and cyclohexane-d(12). Quantum chemical calculations reveal that the cis-conformers of the incipient oxychlorocarbenes C(4)H(7)OC(..)Cl decay to C(4)H(7)Cl + CO via transient hydrogen bonded C(4)H(7)(delta)(+)...Cl(delta-) complexes which possess significant ion pair character, even in the gas phase or in nonpolar solvents. In contrast to benzyloxychlorocarbene, no free radicals are formed upon generation or photolysis of 6 or 10 in Ar matrixes, although acid chlorides (the recombination products of these radical pairs) are observed. The IR spectra obtained in these experiments show the presence of several conformers of the two C(4)H(7)OC(..)Cl.