Sulphenes with carbonyls

Reaction of the carbanion of chloromethyl phenyl sulphoxide 409 with carbonyl compounds yields the corresponding 0-hydroxy adducts 410 in 68-79% yield. Each of these compounds appears to be a single isomer (equation 242). Treatment of adducts 410 with dilute potassium hydroxide in methanol at room temperature gives the epoxy sulphoxides 411 (equation 243). The ease of this intramolecular displacement of chloride ion contrasts with a great difficulty in displacing chloride ion from chloromethyl phenyl sulphoxide by external nucleophiles . When chloromethyl methyl sulphoxide 412 is reacted with unsymmetrical ketones in the presence of potassium tcrt-butoxide in tert-butanol oxiranes are directly formed as a mixture of diastereoisomers (equation 244). a-Sulphinyl epoxides 413 rearrange to a-sulphinyl aldehydes 414 or ketones, which can be transformed by elimination of sulphenic acid into a, 8-unsaturated aldehydes or ketones (equation 245). The lithium salts (410a) of a-chloro-/ -hydroxyalkyl... 

Earlier, it was shown that sulphenes, formed by reaction of sulphonyl halides with a base, reacted with alcohols to give sulphonate esters. These same reactive intermediates have also been used for the formation of sultones, by reaction with carbonyl-containing compounds424-428, as shown in equation 98. If the carbonyl compound contains an a-... 

Paquette et alf have shown that the well-known reaction of sulphenes with vinyl amines to form thietan dioxides is amenable to asymmetric induction. The reaction of the parent sulphene with electronegatively substituted carbonyl compounds can follow two courses (see Scheme 1),... 

Reactions.—A variety of interesting and useful syntheses have been published involving the reaction of dimsyl anion [MeS(0)CHa ] with esters and lactones,with disulphides, with chlorosilanes, with sulphinate esters, with organoboranes, and with stilbenes. Simple and functionalized a-sulphinyl carbanions can be condensed with carbonyl compounds or alkylated, often in a stereocontrolled manner, as in a nicely conceived synthesis of biotin. Considerable attention has been given to methods for the removal of the sulphoxide function following carbon-carbon bond formation. Among the methods used are reduction by aluminium amalgam (with j3-keto-sulphoxides), reduction with Raney nickel, pyrolytic elimination of sulphenic acid, elimination of sulphur dioxide from sultines, e.g. (64), and sulphoxide-... 

Solid samples of S2I2 and SOI2 have been prepared by the reaction74 between HI and S2C12 and SOCl2 respectively, in Freon(II) at —78 °C. The dark brown solids are only stable below — 30 °C and in the absence of water. Nucleophilic substitution at the carbonyl carbon atom in C1C(0)SC1 has been shown75 to be more rapid than at the carbon atom in FC(0)SC1. The S—Cl bond of both sulphenic acid chlorides shows no noticeable difference in reactivity. Although amines react with C1C(0)SC1 at the carbonyl carbon, FC(0)SC1 is attacked at the S—Cl bond. 

Classically, imines have been obtained via derivatisation of carbonyl compounds although problems exist in the use of unreactive carbonyl compounds and/or volatile imines. This transformation has nevertheless been achieved in excellent yields in the absence of solvent merely by treating carbonyl compounds dispersed on alumina with amines that have been similarly dispersed on alumina, Trimethylsily1 trifluoromethanesulphonate has been found to catalyse formation of imines from carbonyl compounds and 1,N-bis-(trimethysilyl )amines, these reactions also proceeding in excellent yield.The same research group also discovered that sulphen-imines could be isolated from reactions between tJ-bis (trimethyl-... 

The structure of benzoylsulphene presents the possibility of reaction by normal 1,2-addition involving the sulphene bond only, or 1,4-addition involving the carbonyl group as well. Reaction with benzylidene-n-propylamine (1 1 ratio of reactants) gave only the 1,4-adduct (88) but... 

Unsaturated Sulphoxides.—Variations of known methods for the synthesis of vinyl sulphoxides are described in reports of asymmetric selectivity in the elimination of HCl from jS-halogenoethyl aryl sulphoxides using an optically active base, leading to partially resolved vinyl sulphoxides, and in reports of the condensation of carbonyl compounds with (Et0)2P(0)CHaS(0)R in the presence of a phase-transfer catalyst. Vinyl sulphoxides are formed when sulphenic acids are trapped after generation in the presence of an acetylenic ester, and a full account is available of the trapping of the sulphenic acid of... 

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