Abstract
A series of substituted hexahydropyrido [2,1‐c][1,4]oxazin‐4(3H)‐ones has been prepared by reaction of the sodio derivative of the appropriate piperidyl carbinol with ethyl chloroacetate. From a study of their NMR spectra the configurations of these compounds have been assigned and the conformation of the perhydro‐1, 4‐oxazinone moiety shown to be that with the ring oxygen atom and the angular hydrogen on the same side of the plane defined by C3C(O)N. The synthesis and NMR spectra of hexahydro‐2H‐pyrido [1,2‐d][1,4]oxazepin‐5(4H)‐one, 1,6,11,11a‐tetrahydro [1,4]‐oxazino [4,3‐b]isoquinolin‐4(3H)‐one and of hexahydropyrido [2,1‐c][1,4]thiazin‐4(3H)‐one are also discussed. cis‐6,9a‐H‐6‐Methyl‐hexahydropyrido[2,1‐c][1,4]oxazin‐4(3H)‐one is shown to exist in a conformation containing a deformed perhydropyridine ring.