Carboxylic esters sulfenylation

Sulfenylation, Sulfonation, and Selenylation of Ketones and Carboxylic Esters... 

MO calculations have been carried out on the isomerization of cyclopropane to propene, and the MNDO method has been used to study the reaction pathway and to optimize the structure of reactant, transition structure, and product of the ring opening reaction of bicyclo[1.1.0]butane. Various methods have been employed to estimate the rate constants for ring opening of the 2-cyclopropyl-2-propyl radical. 1-Acceptor-1-sulfenyl-substituted 2-vinylcyclopropanes of the type (430) have been found to afford 6-sulfenyl-a,jS y, -unsaturated carboxylic esters and nitriles (431) upon treatment with acid, by a process which involves C(l)—C(2) bond fission and a novel 1,5-sulfenyl rearrangement (see Scheme 110). It has been shown that the benzophenone-sensitized photolysis of vinyl norcaradiene derivatives, such as 5-(2-methylprop-l-enyl)-3-oxatricyclo[4.4.0.0 ]deca-7,9-dien-4-ones (432), results in the regioselective cleavage of only one of the cyclopropyl c-bonds to afford isochroman-3-one derivatives (433). It has been reported that the major product obtained from the reaction of structurally diverse a-diazo ketones with an electron-rich alkene in the... 

Buffer catalysis of the hydrolysis of phenyl (311 R = Ph) and methyl (311 R = Me) benzenesulfinates to give the sulfinic acid (312) and alcohol ROH is strongly accelerated by both carboxylate and amine components of the buffer which give Bronsted /i values of approximately unity on separate lines. The carboxylates are about 44 tunes more effective than amines of similar basicity. A concerted. S n2 mechanism with a hypervalent intermediate (313) is proposed for the nucleophilic reaction of these esters.286 The reaction of the thiosulfinate esters (314) with sulfenyl chlorides RSCI and sulfenate esters (315) to give sulfinyl chlorides and disulfides and sulfinate esters and disulfides, respectively, has been studied.287 Hydrolysis of 2-(3-aminophenyl)sulfonyl-ethanol hydrogensulfate gives under different conditions various products such as the ether (316) and the sulfone (317).288... 

Sulfenyl derivatives to protect amines, 251, 377-379 to protect thiols, 303-305 S-Sulfenylthiocarbonate esters, to protect thiols, 303-304 Sulfhydryl groups, see Thiols 4-Sulfobenzyl esters, to protect carboxyl groups, 259-260... 

The sulfmylation of esters, - lactones, carboxylic acids, > amides and lactams may be effected by reacticm of the corresptHiding lithium enolates in THF at -78 to 0 C with dimethyl or difdie-nyl disulfides, or, less conunmily, with methyl or fdienyl sulfmyl halides. The enolates of ketones, however, are insufficioitly nucleq diilic to react with dialkyl sulfides unless HMPA is added to the re-acticm mixture, although they do react smoothly with diaryl sulfides. This difference allows the selective sulfenylation of esters in the presence of ketones (entry 5, Table 3). ... 

Nucleophilic substitution, e.g. the preparation of thiocyanates from lipophilic alcohols, can be facilitated by substrate hydrophilation via ammonioethanesulfonic acid esters (betylates)i . Mercaptans can be easily prepared from alcohols with inversion of configuration via thiolic esters prepared with thioacetic acid in the presence of 2-fluoro-pyridinium salts . C-Sulfenylation of / -dicarbonyl compounds with mercaptans by air oxidation in the presence of tetraethylammonium fluoride has been reported . Activated thiolic and selenolic esters can be prepared at room temperature from carboxylic acids and aryl thiocyanates or selenocyanates in the presence of tri-n-butylphosphine i. Phenylselenolactones have been obtained under very mild conditions from unsaturated acids and benzeneselenyl chloride. ... 

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