Addition of carbenes to 4-methyl-5,6-dihydro-2H- and 4-methylenetetrahydropyrans

It is shown that 4-methylenetetrahydropyran adds a methylene group under the conditions of the Simmons-Smith reaction to give 4,4-dimethylenetetrahydropyran. 4-Methyldihydro-2H-pyran and 4-methylenetetrahydropyran add dichlorocarbene in the presence of a catalyst, viz., triethylbenzylammonium chloride, to give two-ring adducts. It is shown that the adducts can be converted to ketals by refluxing for many hours with alcoholic alkali. The structures of the compounds obtained were established by gas-liquid chromatography and PMR and IR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 167–169, February, 1981.