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First Examples of Reactions of Azole N ‐Oxides with Thioketones: A Novel Type of Sulfur‐Transfer Reaction
Author(s) -
Mlostoń Grzegorz,
Gendek Tomasz,
Heimgartner Heinz
Publication year - 1998
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/(sici)1522-2675(19980909)81:9<1585::aid-hlca1585>3.0.co;2-n
Subject(s) - chemistry , sulfur , transfer (computing) , type (biology) , computational chemistry , organic chemistry , parallel computing , ecology , computer science , biology
The reactions of 1,4,5‐trisubstituted imidazole 3‐oxides 1a – k with cyclobutanethiones 5a , b in CHCl 3 at room temperature give imidazole‐2(3 H )‐thiones 9a – k in high yield. The second product formed in this reaction is 2,2,4,4‐tetramethylcyclobutane‐1,3‐dione ( 6a ; Scheme 2 ). Similar reactions occur with 1 and adamantanethione ( 5c ) as thiocarbonyl compound, as well as with 1,2,4‐triazole‐4‐oxide derivative 10 and 5a ( Scheme 3 ). A reaction mechanism by a two‐step formation of the formal cycloadduct of type 7 via zwitterion 16 is proposed in Scheme 5 . Spontaneous decomposition of 7 yields the products of this novel sulfur‐transfer reaction. The starting imidazole 3‐oxides are conveniently prepared by heating a mixture of 1,3,5‐trisubstituted hexahydro‐1,3,5‐triazines 3 and α ‐(hydroxyimino) ketones 2 in EtOH ( cf. Scheme 1 ). As demonstrated in the case of 9d , a `one‐pot' procedure allows the preparation of 9 without isolation of the imidazole 3‐oxides 1 . The reaction of 1c with thioketene 12 leads to a mixture of four products ( Scheme 4 ). The minor products, 9c and the ketene 15 , result from an analogous sulfur‐transfer reaction ( Path a in Scheme 5 ), whereas the parent imidazole 14 and thiiranone 13 are the products of an oxygen‐transfer reaction ( Path b in Scheme 5 ).