NMR experiments on acetals. 300 MHz spectrum and conformational aspects of the 1‐aza‐4,6‐dioxabicyclo[3.3.0]octane system

Abstract

Abstract-Complete analyses of the 300 MHz 'H NMR spectra of I-aza-4,6-dioxabicyclo[3.3.0]octane (la), the 5-Me-(lb), and both the cis-and trans-3,5-diMe-derivatives (lc and It), as well as most of the corresponding methiodides are reported. Spectral data suggest probable conformations to be 11 (la, l b and lc) and 13 We will first consider compounds l a and l b and their corresponding quaternised derivatives 2a and 2b. Their * Dedicated to the late Mr Th. Lefevre, formerly minister for scientific programmation.

3,7‐Dioxa‐1‐azabicyclo[3.3.0]octanes Substituted at the C‐5 Position − From Local to Global Stereochemistry

“…2 H, 2-H, 8-H-t), 7.34Ϫ7.52 (m, 10 H, Ph) ppm. 13 C NMR (75 MHz, CDCl 3 , 25°C): δ ϭ 9.7 (1 C, CH 2 CH 3 ), 31.4 (1 C, CH 2 CH 3 ), 76.7 (2 C, C-4, C-6), 97.9 (2 C, C-2, C-8), 127.4 (2 C, CH arom. ), 127.6 (4 C, CH arom.…”

NMR experiments on acetals. 51. On the origin of the conformational behaviour of the trimethylammonium substituent: ‐N+Me3substituted 1,3‐dioxanes and ‐CH2N+Me3substituted 1,3‐dioxolanes and 1,3‐dioxanes

“…N+Me3-1, 3-dioxane and c&-2-Me-5-N+Me3-1, 3-dioxane a 3 JN+,H4a= 3.5 Hz, a value that would be much smaller if 5-N+Me3 is equatorial ( 6 ) .…”