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Compounds with bridgehead nitrogen. 44—the conformational analysis of perhydropyrido[1,2-c] [1,3]thiazine

✍ Scribed by Trevor A. Crabb; Philip A. Jupp; Yoshito Takeuchi

Publisher
John Wiley and Sons
Year
1982
Tongue
English
Weight
270 KB
Volume
20
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

The 270 MHz NMR data on trans‐ and cis‐(H‐4a, H‐7)‐7‐ethylperhydropyrido[1,2‐c][1,3]thiazine show heavy conformational bias to the trans‐ and S‐inside cis‐fused conformations, respectively. Comparison of the ^13^C NMR spectra of these anancomeric systems with the ^13^C NMR spectrum of perhydropyrido[1,2‐c][1,3]thiazine indicates a trans‐⇌S‐inside cis‐conformational equilibrium for the latter compound in CDCl~3~ at 25°C, containing ca 75% trans‐fused conformer. The ^13^C NMR spectrum of perhydropyrido[1,2‐c][1,3]‐thiazine at −75°C showed 64% trans‐fused conformer and 36% S‐inside cis‐conformer.

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