Di‐ and Trispirocyclopropanated Tetrahydropyridinones

A variety of spirocyclopropane‐annelated tetrahydropyridinones of types 14 / 15 and 18 / 19 have been prepared in good yields (68−80%) by means of 1,3‐dipolar cycloadditions between nitrones 25 , 31 , and 34 and cyclopropylidenespiropentane ( 7 ) and 7‐cyclopropylidenedispiro[2.0.2.1]heptane ( 8 ), with subsequent thermal rearrangement. While the overall reactions of nitrones 25 and 31 with 7‐cyclopropylidenedispiro[2.0.2.1]heptane ( 8 ) occurred with the commonly observed regioselectivity (i.e., the initially formed cycloadducts of type 12 / 13 rearranged to give compounds 29 , 30 , and 33 as major products), the reactions of 31 and 34 with cyclopropylidenespiropentane ( 7 ) and of 34 with 7‐cyclopropylidenedispiro[2.0.2.1]heptane ( 8 ) showed an opposite trend. Thermal rearrangement of compound 27 gave a mixture of pyridinone 29 and ring‐opened product 30 (19 and 58% yields, respectively). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)