Diastereoselective self-organization of acetylene and acetophenone molecules into 1-benzoyl-3-hydroxy-cyclopentene in the presence of potassium hydroxide

We have recently found that acetylene and alkyl aromatic and alkyl heteroaromatic ketones in the superbasic system KОН–DMSO (80С, 1 h) underwent instead of Favorskii reaction a unique selective tandem reaction leading in a single preparative stage to the formation of complex functionalized heterocyclic systems with a frontalin scaffold, 7-methylene-6,8dioxabicyclo[3.2.1]octanes in up to 86% yield [1]. Since frontalin and its analogs are well known insect pheromones [2, 3] and mammal hormones [4, 5], this easy stereoselective (a single diastereomer forms among many possible) and one-pot approach to their derivatives opens new opportunities for the development of their preparative chemistry. At the same time the yet unknown aspect of acetylene reactivity has been unexpectedly revealed: Its capability in the presence of strong bases to undergo self-assembly with the capture of suitable nucleophiles into complex difficultly available functionalized molecules often structurally close to naturally occurring substances. Here we preliminary report that at the systematic investigation of the above mentioned reaction by an example of acetophenone we have found an entirely new direction of self-assembly of two acetylene and two acetophenone molecules affording along with the expected 7-methylene-6,8-bicyclo[3.2.1]octane (I) also 1-benzoyl-3-hydroxycyclopentene (II), also in the form of a single diastereomer (Scheme 1). The preparative yield of structural isomers I and II was 43 and 46% respectively at the acetophenone conversion 46% (the conditions were not yet optimized).