✍ Scribed by Perjési, PÁL ;Földesi, András ;Szabó, Dezsö ;Zschunke, Adolf ;Mák, Marianna
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While the acid-catalyzed reaction of a$-unsaturated carbonyl compounds with thiourea has been known for long'), the similar reaction of cyclic thioureas has hardly been investigated. In the only case 2-imidazolidinethione was treated with a$-unsaturated carbonyl compounds in the presence of hydrochloric acid as catalyst; these experiments, however, failed to give the expected 1,3thiazine derivatives 'I.
In continuation of our synthetic and stereochemical investigations on the reactions of cyclic a$-unsaturated ketones with thiocarbonic acid derivatives'), we were interested in elaborating the ring closure of 2-benzylidenecycloalkanones with cyclic thioureas. In these reactions formation of tricyclic 1,3-thiazine derivatives was supposed, which were interesting from both pharmacological and chemical aspects4).
Cyclic thioureas la, b were treated with 2-benzylidenecycloalkanones 2a-c in absolute chloroform in the presence of BF3.0Et2 as catalyst. The progress of the reactions strongly depends on the ring size of both the cyclic thioureas and the a,p-unsaturated ke-
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