Sulfenylation carbonyl compounds

The a-seleno and a-sulfenyl carbonyl compounds prepared by this reaction can be converted to a,P-unsaturated carbonyl compounds (17-11). The sulfenylation reaction has also been used as a key step in a sequence for moving the position of a carbonyl group to an adjacent carbon. ... 

Synthesis of heterocycies, from a-sulfenylated carbonyl compounds ... 

The intermediate a-sulfenyl carbonyl compounds may be alkylated prior to oxidative elimination. Phe-nylsulfenylation of the cw-fused butyrolactone (61), followed by methylation and oxidative elimination, gave the a-methylenebutyroiactone (62) because endocyclic elimination is stericaliy inhibited (Scheme 6). For the tran -fused butyrolactone (63), the alkylation was carried out first to ensure exocyclic elimination (Scheme 1). The intermediate a-sulfinylcarbonyl compounds may also be modified before elimination, the alkylation of keto sulfoxides (64) providing a useful synthesis of a,p-unsaturated -y-keto esters (65 Scheme In some cases the use of an excess of strong base provides a dimetaliated... 

REVIEWS - Useful reviews have appeared entitled "As5nranetric Syntheses" "New applications of Malononltrlle in Organic Synthesis," s "Intramolecular Ene Reaction in Organic Synthesis," and "a-Sulfenylated Carbonyl Compounds in Organic Synthesis." Additional articles summarize stereospecific olefin syntheses, heterocyclic syntheses by benzyne cycllza-tlons, and ring transformations of pyrimidines. ... 

Chiral Auxiliary Chemistry The introduction of a sulfur atom to alkanes through a C—H activation is currently limited to enolizable C—H bonds such as a-sulfeny-lation of carbonyl compounds. Although there are other synthetic routes to a-sulfenylated carbonyl compounds, the preparation of chiral compounds has relied on the chiral auxiliary-assisted diastereoselective thioalkylation. In 1985, Paterson et al. reported that the chiral (9-silylated imide enolates 385 of Evans oxazolidinone could be sulfenylated with high diastereoselectivities by phenylsulfenyl chloride (Scheme 46.44). ... 

Trost BM. a-Sulfenylated carbonyl compounds in organic synthesis. Chem. Rev. 1978 78 363 382. 

Despite the synthetic potential of a-sulfenylated carbonyl compounds, their enantioselective synthesis has been scarcely developed, although this tendency is going to... 

A new stable sulfenylating reagent 3-phenylsulfenyl-2-GV-cyano-imino)thiazolidine 57 has been described. It reacts with amines or thiols to give sulfenamides or disulfides in excellent yields. a-Sulfenylation of carbonyl compounds also proceeds smoothly and if an optically active 4-diphenylmethyl substituent is attached to the thiazolidine ring (58), the cyclic (3-ketoester 59 can be sulfenylated in high yield with an ee of 96% to give the sulfide 60 <00SL32>. 

Insertion of carbon monoxide into Csp2—Zr bonds occurs readily at ambient temperatures or below to produce a,(5-unsaturated, reactive acyl zirconocene derivatives [27—29]. Early work by Schwartz demonstrated the potential of such intermediates in synthesis [5d], as they are highly susceptible to further conversions to a variety of carbonyl compounds depending upon manipulation. More recently, Huang has shown that HC1 converts 16 to an enal, that addition of a diaryl diselenide leads to selenoesters, and that exposure to a sulfenyl chloride gives thioesters (Scheme 4.11) [27,28]. All are obtained with (F)-stereochemistry, indicative of CO insertion with the expected retention of alkene geometry. 

Chloroallyl) thiocarbamate sulfoxides (. ., 5-2) un-.doubtedly rearrange in an analogous manner but in tbis case tbe sulfenate quickly undergoes an additional 1,2-elimination reaction (7 ). Tbe resulting products are tbe IJ, -dialkylcarbamoyl-sulfenyl chloride (M) and tbe carbonyl compound, aldehydes... 

All acetylenes with a terminal triple bond are instantaneously converted into the alkali acetyiides by alkali amides in liquid ammonia. For many alkylations with primary alkyl halides liquid ammonia is the solvent of choice and the functionalization with oxirane can also be carried out in it with good results. Reactions of RC=CM with sulfenylating agents (R SSR R SC=N, R SSC R ) or elemental sulfur, selenium or tellurium are mostly very successful in ammonia, the same holds for the preparation of RCsCI from RGCM and iodine. The results of couplings with carbonyl compounds are very variable. 

For a more comprehensive account of the methods available for the sulfenylation of carbonyl compounds the review by Trost is recommended. ... 

Carbonyl compounds (321) possessing an a-methylene moiety react with l,2-bis(chloro-sulfenyl)alkanes (322) to give 1,3-dithiolanes (323) (Equation (66)) <72JOC887> similarly, 2-alkyl-idene 1,3-dithiolanes are accessible <9lS30l>. 

Sulfenylation of lithium enolates with PhS-SPh or of silyl enol ethers with PhS-Cl allows any a-PhS carbonyl compound to be made regioselectively, e.g. 149 and 152 from 147 (see chapter 5). Oxidation with sodium periodate gives the sulfoxide without over-oxidation to the sulfone, but elimination requires reasonably high temperatures (about 120 °C for MeSO but only about 50 °C for PhSO). Together with the unpleasant by-products, the results of disproportionation of unstable PhSOH, this has led to a preference for the selenium version of the reaction, though we must admit that the by-products are even more offensive.22... 

Thioallylation. Allylzirconium species derived from allenyl sulfides react with carbonyl compounds in an anri-selective fashion to give 4-hydroxy-3-sulfenyl-l-alkenes. 

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