Methylene-1,3-dithietanes reactions

The reaction of 1,3-dithietane 92f substituted with a diethylphosphoryl group with G-nucleophiles is analogous to the previously reported reaction. Its condensation with different C-nucleophiles, such as cyclic and acyclic a-carbonyl-methylenes and a-carbonylhydrazones, gave a number of [2,l-3]fused phosphono-substituted thioxopyranes 97, 100, 103, 107, oxadiazine 109, and thiazine 105 (Scheme 12), which are of potential biological interest <2002PS1885>. 

A similar reaction of the methylene derivatives 194 with carbon disulfide under (PTC) conditions followed by the action of 4,4-dibromo-l-phenylpyrazolidine-3,5-dione 195 produced the spiro-1,3-dithietanes 196 (Scheme 24 Table 10) <2000PS159>. 

The 4-methylene-l,3-dithietane-2-ones lose carbon oxysulfide to give thio-ketenes that dimerize to 2,4-dimethylene-l,3-dithietanes, as exemplified by the flash-vacuum thermolysis of 551. Reaction of several methylene 1,3-dithietane-2-ones with secondary amines also appears to proceed via loss of carbon oxysulfide followed by addition of the amine to the thioketene. An exception to the loss of carbon oxysulfide is the reaction of a guanidine derivative with 551 to give the ring-opened product 552. ... 

The two most common methods of synthesis of methylene-1,3-dithietanes are the reaction of 1,1-dihalides or their equivalents with salts of 1,1-dimercapto-... 

In the reactions of 1,1-dihalides, tin salts of 1,1-dimercaptoalkenes give somewhat better yields (only an 18% yield of 564 is obtained with the disodium salt). The reaction of active methylene compounds with carbon disulfide is a common method for obtaining 1,1-dimercaptoalkene derivatives, as exemplified in the synthesis of 565. The reaction of dimercaptoalkene salts with phosgene yields 2-keto-4-methylene-l,3-dithietanes. 

The most common reaction of 2,4-bis-(methylene)-l,3-dithietanes with nucleophiles involves an apparent Michael addition to an electron-deficient double bond followed by ring-opening. Further reactions may ensue depending on the functional groups present. The reactions of 578 have been extensively investigated. Reactions have been reported with ethoxide ion and thiolate ions, ammonia and amines " " - (e.g., the formation of 579), hydra-... 

Reaction of 2-methylene-1,3-dithietanes (256) with hydrazines affords 5-thiolpyrazoles (257) <90JHC567>. These last products were converted into 5-S-methyl pyrazoles (258) by methyliodide. Other authors <87JCS(P1)1945> have used a-aroyl-a-bromoketenedithioacetals to prepare 3(5),4-bis(alkylthio)pyrazoles. 

Active-methylene compounds are converted into the corresponding thioketones by successive reaction with thionyl chloride and triphenylphosphine. The thioketones thus prepared are too unstable to be isolated, and they undergo dimerization to give the 1,3-dithietans (57)—(59). However, the intermediacy of thioketones has been confirmed by u.v. spectrometry. The transient formation of thioketone and then its dimerization or a Diels-Alder reaction with an olefin has... 

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