THE MANNICH CONDENSATION WITH 1-HETERA-4-CYCLOHEXANONES. THE NOVEL FORMATION OF 7-BENZYL-3-HETERA-7-AZABICYCLO[3.3.1]NONAN-9-ONES, 3,6-DIBENZYL-HEXAHYDRO-8a-METHOXY 5H-4a,8-(METHANO-HETERAMETHANO)-2H-PYRIDO[3,4-e]-1,3-OXAZINES, AND 2,4,10,12-TETRABENZYL-2,4,10,12-TETRAAZA-15-HETERADISPIRO[5.1.5.3]HEXADECAN-7-ONES. SINGLE CRYSTAL X-RAY DIFFRACTION ANALYSES OF 3,6-DIBENZYLHEXAHYDRO-8a-METHOXY-5H-4a,8-(METHANOTHIOMETHANO)-2H-PYRIDO[3,4-e]-1,3-OXAZINE AND 2,4,10,12-TETRABENZYL-2,4,10,12-TETRAAZA-15-THIADISPIRO[5.1.5.3]HEXADECAN-7-ONE

Abstract

Abstract We report for the first time the formation of unusual multicyclic products from the condensation of 1-hetera-4-cyclohexanones in a Mannich reaction with benzylamine, formaldehyde, and acetic acid in methanol. In addition to the expected ketones, namely 7-benzyl-3-hetera-7-azabicyclo[3.3.1]nonan-9-ones, there were obtained from 4-thianone and 4-selenanone the following systems. Repeated Mannich condensations produced 3,6-dibenzylhexahydro-8a-(methoxy-5H-4a,8-(methanothiomethano)-2H-pyrido[3,4-e]-1,3-oxazine, 3,6-dibenzylhexahydro-8a-methoxy-5H-4a,8-(methanoselenomethano)-2H-pyrido[3,4-e]-1,3-oxazine, 2,4,10,12-tetrabenzyl-2,4,10,12-tetraza-15-thiadispiro[5.1.5.3]-hexadecan-7-one, and 2,4,10,12-tetrabenzyl-2,4,10,12-tetraza-15-selenadispiro[5.1.5.3]hexadecan-7-one. Single crystal X-ray diffraction analysis confirmed the structures of the first three solids. Using tetrahydro-4H-pyran-4-one, it was possible to obtain 7-benzyl-3-oxa-7-azabicyclo[3.3.1]nonan-9-one and 2,4,10,12-tetrabenzyl-2,4,10,12-tetraaza-15-oxadispiro[5.1.5.3]hexadecan-7-one. To the best of our knowledge, these systems have not been previously recorded, and the method reported herein is a one-step approach. NMR analyses, including 1H, 13C, and 15N analyses, were completed and support all of the structures described herein. A mechanism is briefly outlined to explain the formation of these novel polycyclic heterocycles.