Sulfides vinyl, hydrolysis

Many of these reactions are reversible, and for the stronger nucleophiles they usually proceed the fastest. Typical examples are the addition of ammonia, amines, phosphines, and bisulfite. Alkaline conditions permit the addition of mercaptans, sulfides, ketones, nitroalkanes, and alcohols to acrylamide. Good examples of alcohol reactions are those involving polymeric alcohols such as poly(vinyl alcohol), cellulose, and starch. The alkaline conditions employed with these reactions result in partial hydrolysis of the amide, yielding mixed carbamojdethyl and carboxyethyl products. 

Add hydrolysis of l-ethylthiobut-l-en-3-yne (143) (10% sulfuric acid, 60-95°C) mainly involves hydration of the triple bond (evidently due to the greater hydrolytie stability of the vinyl sulfide moiety of the moleeule), whieh results in the formation of l-ethylthiobut-l-en-3-one (144). The latter is further hydrolyzed to aeetoaeetie aldehyde (132) (75IZV1975 78IZV153). 

Chemical/Physical. In an aqueous phosphate buffer solution (0.05 M) containing hydrogen sulfide ion, ethylene dibromide was transformed into 1,2-dithioethane and vinyl bromide. The hydrolysis half-lives for solutions with and without sulfides present ranged from 37 to 70 d and 0.8 to 4.6 yr, respectively (Barbash and Reinhard, 1989). Dehydrobromination of ethylene dibromide to vinyl bromide was observed in various aqueous buffer solutions (pH 7 to 11) in the temperature range of 45 to 90 °C. The estimated half-life for this reaction at 25 °C and pH 7 is 2.5... 

Hydrolysis is probably a more complex process, since 3,4-bis(trifluoro-methyl)perfluorohexa-2,4-diene gives a cyclic product—perfluorotetra-methylfuran 46 (94JCS(P1)3119, 90JCS(CC)1127). The reaction involves vinyl substitution of fluorine with subsequent fast electrocyclization of the intermediate carbanion accompanied by fluoride ion elimination. An analogous reaction of 3,4-bis(trifluoromethyl)perfluorohexa-2,4-diene with sodium sulfide or thiourea forms perfluorotetramethylthiophene 47 (90JCS(CC)1127). 

Other lithiated vinyl sulfides bearing a carbonyl group at the / -position have been used in organic synthesis mainly as /3-acyl vinyl anion equivalents858. The 2-(isopropylsulfanylmethylene) derivative 673 has been deprotonated with lithium 2,2,6,6-tetramethylpiperidide (LiTMP) to give the intermediate 674 which, after addition to methyl acrylate and final hydrolysis, afforded the cyclopentenone 675 in 70% overall yield981 (Scheme 175). 

Vinyl cyanides may be useful derivatives since permanganate-induced a-hydroxylation in the presence of alkenes has been demonstrated, e.g. (90) to (91). Oxygenation of a,B-unsaturated vinylsilanes and sulfides using the previously described procedures wo d not be successful (Sections 2.3.2.1. S.iii and 2.3.2.l.S.iv). However a singlet oxygen cycloaddition process (cf. Section 2.3.2.2.3.ii), followed by eliminative hydrolysis, could provide a usable, although lengthy, approach (Scheme 18). 

In one case the cycloaddition product could only be reduced to (—)-8a-epidesacetoxy-slaframine, as the hydrolysis of the vinyl sulfide to the ketone proved unsuccessful94. 

Another advantage over other Lewis acids is the thiophilic nature of copper this has led to its utility in the hydrolysis of thioacetals. Copper(II) chloride in conjunction with copper(II) oxide was introduced by Mukaiyama [16] for the deprotection of 1,3-dithianes and this method has found utility in a variety of synthetic protocols (Sch. 6) [17]. This combination, in which copper oxide plays the role of a buffer to prevent the medium from becoming too acidic, has also found application in the hydrolysis of a-heteroatom substituted and vinyl sulfides [18]. Acetals, which are prone to epimerization under acid-catalyzed hydrolysis conditions (21), can be con-... 

The vinylogous thioacetal 33 was transformed into the a,(8-unsaturated ketone 34 upon CuOTf-mediated hydrolysis whereas the HgCl2-promoted reaction was less effective (Sch. 9) [27]. Similarly, vinyl sulfide 35, which bears an allylic alcohol, was converted into the aj3-unsaturated ketone 36 with complete regiocontrol [28]. This regioselectivity is not dependent upon the heteroatom because the vinyl ether 37 hydrolyzes to the aldehyde or ketone 38 [29]. 

A simple and straightforward application was outlined in the synthesis of hydrohydrastinine as depicted in Scheme 10. Michael addition of 3,4-methyle-nedioxyphenylmethyl amine to vinyl sulfoxide 36 took place smoothly in refluxing methanol. Pummerer rearrangement in acetic anhydride afforded acetoxysulfide 37 in 90% yield and this was then cyclized to 38 with BF3 etherate in 93 % yield. Sulfide 38, which was rather unstable, was desulfurized with Raney nickel in 80 % yield. Hydrolysis of the acetyl group followed by reductive methy-lation afforded hydrohydrastinine (39) in good yield [24]. 

Full details for preparation of this tetravalent iodine compound arc now available.1 Since explosions have been reported in the preparation, the directions should be followed with care. Moreover, the reagent is sensitive to moisture, which converts it into iodosylbenzoic acid, also reported as explosive. The periodinane oxidizes primary and secondary alcohols rapidly and efficiently to carbonyl compounds without further oxidation to acids. Bcnzylic and allylic alcohols can be selectively oxidized. It does not react with sulfides or vinyl ethers. The iodine-containing by-product can be removed by hydrolysis to 2-iodosylbcnzoic acid. 

Lower dialkyl sulfides and vinyl sulfides293 are advantageously prepared by alkaline hydrolysis of S-alkylthiouronium salts, the resulting thiolate being alkylated, without isolation, by an alkyl halide or dialkyl sulfate.294... 

Hydrolysis of vinyl sulfides to carbonyl compounds. Corey and Shulman (3, 97) in 1970 fhst reported that vinyl sulfides could be hydrolyzed to ketones with mercuric chloride in aqueous acetonitrile. This method, sometimes in combination with mercuric oxide or calcium carbonate (4, 38, 39), has been widely used. However, recently, Grieco, Cohen, and collaborators have reported that mercuric chloride hydrolysis of vinyl sulfides of type (1) to aldehydes is not generally successful. They have found a very simple solution illustrated for hydrolysis of (2) to n-heptanal (4). 

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