Cycloadditions of Nitrile Oxides and Nitrones to 4,4-Methylene-1-methylpiperidine: Studies in Regio- and Stereoselectivity

Article abstract of DOI:10.1007/BF00811848

A series of spiro-substituted isoxazole derivatives were synthesized by 1,3-dipolar cycloadditions of nitrile oxides and nitrones to 4,4-methylene-1-methylpiperidine.Since nmr studies confirmed that only one regioisomer was formed selectively, semi-empirical quantum mechanical methods (AM1) were used to rationalize this regiochemical preference via calculation and inspection of HOMO-LUMO-energy and coefficients.X-ray structure analysis carried out for one of these products showed the occurrence of only one stereoisomer, explicable by comparing AM1-calculated ΔH_f-values of all possible cycloadducts. - Keywords: 1,3-Dipolar cycloaddition; Nitrile oxide; Nitrone; 4,4-Methylene-1-methylpiperidine; AM1 calculations.