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Compounds with bridgehead nitrogen. 57 —NMR spectra and stereochemistry of protonated perhydrooxazolo [3,4‐ a ]pyridines, perhydropyrido[1,2‐ c ] [1,3] oxazine and perhydropyrido[1,2‐ c ] [1,3]oxazepine
Author(s) -
Crabb Trevor A.,
Trethewey Andrew N.
Publication year - 1988
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260260905
Subject(s) - chemistry , conformational isomerism , protonation , pyridine , nitrogen , base (topology) , cis–trans isomerism , nmr spectra database , diethyl ether , ether , medicinal chemistry , spectral line , stereochemistry , organic chemistry , molecule , ion , mathematical analysis , physics , mathematics , astronomy
Protonation of perhydrooxazolo[3,4‐ a ]pyridine, perhydropyrido[1,2‐ c ][1,3]oxazine and perhydropyrido[1,2‐ c ][1,3]oxazepine by hydrogen chloride gas in diethyl ether gave mixtures of trans ‐ and cis ‐fused hydrochlorides containing 28, 75 and 79% of the trans ‐fused salts, respectively, which compare with free base equilibria containing 68, 90 and 74% trans ‐fused conformers. The cis ‐fused salts from perhydrooxazolo[3,4‐ a ]pyridine existed in solution (CDCI 3 , 298 K) as an equilibrium containing 55% O ‐inside cis ‐ and 17% O ‐outside cis ‐fused conformers. Similar mixtures, but with smaller percentages of cis ‐fused salts, were formed in D 2 ODCI.