Unusual reaction of 3,6-dimethoxy-benzonorbornadiene with 2-chloro-sulfenyl-1-pyridine 1-oxide

Abstract

In reactions of 3,6-dimethoxybenzonorbornadiene (1) with sulfenyl chlorides, usually mixtures of 1,2-addition and Wagner-Meerwein rearrangement products are obtained, and the yield of rearrangement products is significantly increased in the presence of salt additives [1,2].We have found that the primary direction of the reaction of the unsaturated compound 1 with 2-chlorosulfenyl-1-pyridine 1-oxide (2) in methylene chloride at 20°C is polar exo-cis cycloaddition of the sulfenylating reagent at the multiple bond, with closure of the ring by the oxygen atom of the N-oxide group and formation of polycyclic system 3a in 45% yield. The other direction of the reaction, the Wagner-Meerwein rearrangement, leads to γ-chloro sulfide 4, the yield of which is 34%. Formation of exclusively the product of polar cycloaddition 3b (the perchlorate analog of salt 3a) in 82% yield occurs upon sulfenylation of compound 1 in nitromethane in the presence of lithium perchlorate. OMe MeO N SCl O N O S OMe MeO Cl O S N MeO OMe + 1 2 CH 2 Cl 2 3b Cl _ + 3a _ + 4 MeNO 2 LiClO 4 _ + +Thus even under conventional conditions, sulfenyl chloride 2 reacts with unsaturated compound 1 preferentially according to a [4 + + 2] cycloaddition scheme [3]. To our knowledge, such data for reactions of sulfenyl chlorides with alkenes were obtained for the first time in [4][5][6][7].

Synthesis of novel heterocyclic systems. 2,3-dihydropyrido[1,2-b][1,4,2]oxaselenazin-5-ium

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We have recently proposed a method for the synthesis of the novel 2,3-dihydropyrido[1,2-b][1,4,2]-oxathiazinium-5 heterocyclic system based on the heterocyclization of 2-chlorosulfenyl-1-pyridine 1-oxide with unsaturated compounds [1][2][3][4]. As far as we known, analogous selenium containing heterocycles have not been prepared to this time.

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