Sulfenic acid, synthesis

Protection of carboxyflc acids and sulfenic acids requires efficient sdyl donors, eg, BSA, MTSA, and bis(ttimeth5isdyl)urea [18297-63-7] (BSU). BSU is often prepared in situ from hexamethyldisda2ane and urea to yield over 90% of the sdylated derivative in synthesis of cephalosporins (5). 

The addition of sulfenic acids to olefins207 has been successfully applied in the synthesis of thietanoprostanoids, the thietane analogues of prostaglandin245. The general synthetic scheme is presented in equation 83207. The key step is the thermolysis of either erythro- or (7ireo-2-f-butylsulphinyl-3-vinyl-l-ol (209) to give the corresponding alkenesulfenic acids 210, which cyclize spontaneously to a mixture of stereoisomeric thietane oxides. 

Jones and Lewton250 have also demonstrated the utility of the intramolecular addition of sulfenic acids to olefins as a stereospecific method for the synthesis of thiolan 1-oxides. 

Taking advantage of a tandem sulfoxide elimination-sulfenic acid addition approach to cyclic sulfoxides <1977J(P1)1574>, the synthesis of a number of novel 1,4-oxathiane oxides 229 and 230 based on the intramolecular addition of sulfenic acids to alkenes or alkynes tethered through an ether linkage has been reported (Equation 38) <20050BC404>. 

Saito et al. <1995S87> described a new method for the synthesis of heterocycle-fused[c]thiophenes via reaction of aryl heteroaryl thioketones with the carbene precursors. Heteroaromatic thioketones A react with carbenoids generated from bis(arylsulfonyl)diazomethanes or phenyliodonium bis(phenylsulfonyl)methylides to give heterocycle-fused[f]thiophenes B. The reaction involves the ring closure of the intermediary thiocarbonyl ylides, followed by restorative aromatization via the elimination of a sulfenic acid (Equation 11). 

One Hundred Years of Sulfenic Acid Chemistry II, Substitution and Cyclization Reactions of Sulfenyl Halides E. Kuehle, Synthesis, 1971, 617-638. 

Recently, it has been reported that sulfenic acids add readily to 1-alkynes to give a,(3-unsaturated sulfoxides,556 themselves useful for the synthesis of various cyclopentenones (equation 307).557... 

The first highly stereocontrolled total synthesis of a natural penicillin was reported 2 years later by Baldwin et al. <1976JA3045>. In this case, the methodology relies on the formation of the fi-lactam ring before the thiazolidine ring closure, via the sulfenic acid intermediate 97 (Rz = OH), which gives electrophilic attack on the double bond to produce a penam sulfoxide 98 (see Section 2.03.5.3) (Scheme 52). A similar route has been developed independently by Kishi for the total synthesis of 6cr-methoxy penicillin derivatives <1975JA5008>. 

When applied to whole HeLa cells, 193 proteins were identified, with diverse biological functions including signal transduction, protein synthesis, and chaperone-mediated protein folding. Of the proteins identified in this study, 56% were not previously reported to possess redox-active cysteines, and 93% were not reported to undergo sulfenic acid modification [172]. 

Reactions of 112 (R = H) with divinyl benzenes and naphthalenes have allowed the enantioselective synthesis of helicenebisquinones in high optical purity (80-88% ee) [118b]. In Scheme 66 is also depicted the results obtained from 1,4-divinyl naphthalene. The formation of (M)-(-)-133 involves a sequential process consisting of the cycloaddition of 112, pyrolytic sulfenic acid elimination, and final aromatization, in each of the two dienic moieties of the starting naphthalene. 

Ishii A, Komiya K, Nakayama J (1996) Synthesis of a stable sulfenic acid by oxidation of a sterically hindered thiol (thiophenetriptycene-8-thiol) and its characterization. J Am Chem Soc 118 12836-12837... 

The utility of intramolecular addition of sulfenic acids to alkenes as a stereoselective method for the synthesis of various sulfoxides has also been demonstrated. Thus, heating 5-tert-buXy -sulfinyl-l-pentene or 6-tm-butylsulliny 1-1-hexene at 140-160°C gives ds-2-methylthiacy-cloalkanes 2 exclusively91. 

A mercury-free route to allyl vinyl ethers that relies on the Michael addition of allyl alcohols to unsubstituted alkenyl sulfoxides, followed by thermal loss of sulfenic acid and concurrent Claisen rearrangement has been described [145]. This methodology has been applied to the synthesis of isocar-bacyclin [146]. Posner reported an acid-catalyzed protocol that produces conjugated dienoate esters from allylic alcohols and a sulfinyl orthoester [147]. Additionally, the use of propargyl alcoholates and a chloro alkenyl sulfox-... 

Vinyl sulfoxides mostly require a second electron-withdrawing groiq) to increase their dienophilic character. Thus vinyl sulfoxides bearing a carbonyl moiety at Cp undergo carbonyl-directed diene addition followed by a spontaneous elimination of sulfenic acid, as applied to a synthesis of disodium pre-phenate (74) (Scheme 21). ... 

Sulfoxides fragment on heating to form alkenes and sulfenic acids. This reaction, known for over a century, has been developed into a useful alkene synthesis, - particularly for the synthesis of a,p-un-saturated carbonyl compounds as illustrated in equations (16)-(18). ... 

So far in this chapter sulfoxide pyrolysis has been discussed in connection with alkene synthesis. However, the other products of these reactions, the sulfenic acids, are also of interest, and have been generated for study by several methods including sulfoxide pyrolysis. Thermolysis of di-f-butyl sulfoxide (79 ... 

Stilbenes synthesis by Heck coupling, 43 Stille coupling aryl triflate + organylstannane, 42 Stobbe condensation, 58-59 Stork reagent, 328-329 Strain, steric. See Steric strain Strecker s synthesis of a-amino acids, 50, 301 L-Streptose synthesis, 267 Styrene. See Benzene, ethenyl-Succinic acid. See Butanedioic acid Succinimide. See 2,5-Pyrrolidinedione Sugars. See Monosaccharides Oligosaccharides inexpensive derivs. pr. (table), 263-264 Sulfafurazole, 307 Sulfamethoxazole, 308 Sulfenic acids, esters ... 

Topics which have formed the subjects of reviews this year include excited state chemistry within zeolites, photoredox reactions in organic synthesis, selectivity control in one-electron reduction, the photochemistry of fullerenes, photochemical P-450 oxygenation of cyclohexene with water sensitized by dihydroxy-coordinated (tetraphenylporphyrinato)antimony(V) hexafluorophosphate, bio-mimetic radical polycyclisations of isoprenoid polyalkenes initiated by photo-induced electron transfer, photoinduced electron transfer involving C o/CjoJ comparisons between the photoinduced electron transfer reactions of 50 and aromatic carbonyl compounds, recent advances in the chemistry of pyrrolidino-fullerenes, ° photoinduced electron transfer in donor-linked fullerenes," supra-molecular model systems,and within dendrimer architecture,photoinduced electron transfer reactions of homoquinones, amines, and azo compounds, photoinduced reactions of five-membered monoheterocyclic compounds of the indigo group, photochemical and polymerisation reactions in solid Qo, photo- and redox-active [2]rotaxanes and [2]catenanes, ° reactions of sulfides and sulfenic acid derivatives with 02( Ag), photoprocesses of sulfoxides and related compounds, semiconductor photocatalysts,chemical fixation and photoreduction of carbon dioxide by metal phthalocyanines, and multiporphyrins as photosynthetic models. 

Cycloaddition of the diene 20 with dienophiles bearing a phenyl sulfoxide substituent leads, after elimination of phenyl sulfenic acid and hydrolysis, to a 4,4-disubstituted cyclohexadienone or a substituted phenol product. For example, an elegant synthesis of disodium prephenate 34 makes use of this chemistry... 

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