ADDITION-REARRANGEMENT OF ARYLSULFONYL AND ALKOXYSULFONYL ISOCYANATESWITH 5-METHYL-SUBSTITUTED 3,4-DIHYDRO-2-METHOXY-2H-PYRANS - SELECTIVESYNTHESIS OF FUNCTIONALIZED 2-PIPERIDONES

3,4-Dihydro-2-methoxy-5-methyl-2H-pyran and 3,4-dihydro-2-methoxy-5,6- dimethyl-2H-pyran undergo addition-rearrangement reactions with arylsu lfonyl isocyanates to generate the corresponding 3-formyl- and 6-metho xy-3-methyl-1-(arylsulfonyl)-2-piperidones. For example, 3,4-dihydro-2 -methoxy-5-methyl-2H-pyran and phenylsulfonyl isocyanate afforded 6-me thoxy-3-methyl-1-(phenylsulfonyl)-2-piperidone as a separable trans/ci s mixture in high yield. The more reactive phenoxysulfonyl and alkoxys ulfonyl isocyanates provided analogous results.