HALOMETHYL-METAL COMPOUNDS .25 ALPHA-POLHALOALKYLTIN COMPOUNDS AS HALOCARBENE PRECURSORS

The thermolysis of a number of halomethyl-tin compounds in the presence of olefins has been investigated. Trimethyl(trichloromethyl)tin was found to be an effective CCl2 transfer agent at 140°, and the action of sodium iodide in 1,2-dimethoxyethane at 85° induced CCl2 transfer from this tin compound in fair yield. Trimethyl-(bromodichloromethyl)tin transferred CCl2 to olefins very slowly at 80°, rapidly at 140°, but a small amount of decomposition to give Me3SnCl and CClBr also was noted. In contrast, trimethyl(dichloromethyl)tin proved to be very stable thermally and it did not transfer CHC1 at 140°. Trimethyl(α,α-dichlorobenzyl)tin appeared to transfer PhCCl to tetramethylethylene, but the initially formed cyclopropane was not isolated. Instead, 2,4-dimethyl-3-phenylpenta-1,3-diene, a product derived from ring opening of the latter and subsequent loss of hydrogen chloride, was obtained in 34% yield. When trimethyl α,α-dichlorobenzyl)tin was pyrolyzed in the presence of cyclohexene, the major products were dimethyltin dichloride and styrene, and their formation could be explained in terms of a (Me→ C, CI→Sn) interchange in Me3SnCCl2Ph before α elimination of a tin chloride. In the pyrolysis of bis(trimethyltin)bromochloromethane in the presence of cyclohexene at ca. 170°, the formation in low yield of 7-chloro-7-trimethyltinnorcarane, bis(3-cyclohexenyl)methane, and 7,7ʹ-bi(bicyclo[4.1.0]heptane) spoke for trimethyltinhalocarbene intermediates in the decomposition process. A similar reaction with bis(trimethyltin)-dibromomethane gave only 7,7ʹ-bi(bicyclo[4.1.0]heptane), while bis(trimethyltin)dichloromethane was quite stable thermally. © 1969, American Chemical Society. All rights reserved.