Sulphenes reactions with enamines

Enamines reaction with methanesulphonyl chloride and its homologues in the presence of triethylamine to yield thietane 1,1-dioxides. Thus 1-morphoIinocyclohexene gives a bicyclic thietane dioxide and 2-methyl-l-pyrrolidinopropene and other enamines derived from aliphatic aldehydes react analogously (equation 1). It is thought that the reactions proceed by way of the unisolable sulphene 1, which adds to the enamine double bond in a stepwise or concerted manner. This question has been much debated (for a critical discussion, see Reference 2, p. 3386) and will not be pursued here. It has been found that there is a lack of stereoselectivity in the addition of sulphene to the conformationally rigid enamines derived from 4-t-butylcyclohexanone . 

The thieten 1,1-dioxide (48) has been prepared by cycloaddition of an enamine and sulphene at 0°C. Mild thermolysis causes a ready retrocyclo-addition to occur. Additional stable 3-sultines have been isolated, by the reaction of the anion of a sulphoxide with a ketone and cyclization of the resulting j3-hydroxy-sulphoxide with sulphuryl chloride. Treatment of 2-methylthietan (49) with alumina at 150-350 °C results in the formation of tetrahydrothiophen and but-3-enethiol. ... 

Formation.—The use of sulphenes in the synthesis of thietan 1,1-dioxides has been reviewed. -The formation of thietan 1,1-dioxides from enamines and sulphenes and the stereoselectivity of the reaction is discussed in Chapter 3, Section 2 (p. 140). When a mixture of cis- and /ro j-2-chloro-2,4,4-trimethyl-3-dialkylaminothietan 1,1-dioxides is treated with aqueous alkali, the c/j-isomer is converted into the thietan-3-one, leaving the pure rra/ij-isomer untouched. Cyclic a-amino-ketoximes can be converted in one step into... 

The synthesis and properties of optically active thiet 1,1-dioxides have been reviewed. The generation of sulphenes from p-nitrophenyl sulpho-nates is claimed to have advantages in the preparation of 3-amino-4-arylthiet 1,1-dioxides from acetylenic amines, principally in the avcndance of the presence of triethylamine hydrochloride, which is believed to cause isomerization of the thiet derivative. Several other thiet dioxides have been obtained by reaction of a sulphene with an acetylenic amine. - They are claimed to be anti-inflammatory agents. The formaticm of a thiet 1,1-dioxide from acetylenic sulphine (167) and an enamine has been noted previously. A number of substituted thiet dioxides have been prepared by addition of sulphene to enamines followed by a Cope elimination of the amine. These compounds were tested for analgesic activity but none was found. Thiet 1,1-dioxide (123) is obtained from... 

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