108235-27-4Relevant articles and documents
A New Route to Cyclazines
Batroff, Volker,Flitsch, Wilhelm
, p. 621 - 628 (2007/10/02)
In search of routes to 5b,7a-dihydrocyclobutacyclazines 2, which should be starting materials for a photochemical synthesis of the diradicaloid cyclazine (1), cycloaddition reactions of indolizines 8 with electron-deficient olefins and acetylenes in the absence of dehydrogenating reagents have been studied.The tetracyclic compound 9 was obtained from 8b and 1-cyclobutene-1,2-dicarbonitrile.Upon oxidation 9 was rearranged to yield the cyclazine 10. - The cycloadducts 6a and b have been obtained from the reaction of dimethyl maleate with the indolizines 8b and c.The compounds 6a and b were transformed into the cyclic thioethers 22 on conventional routes.A Stevens rearrangement of 22b, intended to result in a ring contraction, gave the 3,5-divinyldihydroindolizine 24 in good yields.Cycloaddition reactions of dimethyl acetylenedicarboxylate and indolizines 8 yielded the cyclazine derivatives 3 and 4a-c.
