Author:
Kristensen J.,Thomsen I.,Lawesson S. ‐O.
Abstract
Abstract2‐Bromo‐2‐methylpropylidene malonates, 3, undergo thermal ringclosure reactions to give 3‐alkoxycarbonyl‐5,5‐dimethyl‐2(5H)‐furanones, 4. Michael addition of Grignard reagents and thiols to 4a, subsequent ethoxycarbonyl elimination, treatment of 8 with SOCl2 and EtOH and, finally, ringclosure lead to cyclopropanes. Sodium cyanide is also smoothly added to 4a. Addition of NaCN, C2H5ONa and ϕSNa to 3 gives the cyclopropanes, 17. Subsequent ethoxycarbonyl elimination of 17a produces 18a and 19a, which are related to chrysanthemic acid.