13C, 1H long‐range coupling constants in configuration assignment of some trisubstituted alkenes

Chemical shifts and long‐range 13C, 1H coupling constants to the two carbonyl C atoms were determined for a series of ethyl 2‐acyloxy‐2‐alkenoates. The 3J(C,H) coupling constant across the double bond is 9.5–10.1 Hz for the E‐ and 2.9–3.8 Hz for the Z‐isomer. 3J(C,H) values, therefore, may be used as a criterion for E/Z differentiation even if only one isomer is available. 13C chemical shift data, in contrast, cannot be employed for a straightforward differentiation.