Phenylsulfonyl acetalization with

We begin with studies of the pKa values of substituted phenylmercapto-, phenylsulfinyl-and phenylsulfonyl-acetic acids. Pasto and Kent136 found that phenylsulfinylacetic acid was a weaker acid than phenylsulfonylacetic acid in water, the pKa values at 25 °C being 2.732 and 2.513 respectively. However, in aqueous ethanol or aqueous dioxan as solvent... 

Charton s at values for SOPh and S02Ph are based on the pKa values for phenylsulfinyl- and phenylsulfonyl-acetic acids137, which we have already discussed in connection with the transmission of electronic effects by SO and S02 (Section III.C). These groups have also been the subject of a detailed study by Hogeveen and Montanari172, who measured the pKa values of some 3-phenylthio-, 3-phenylsulfinyl- and... 

Allylic acetates of either geranyl acetate or neryl acetate reacted with the sodium salt of methyl phenylsulfonyl acetate in the presence of tetrakis(triphenylphosphine palladium) affording the corresponding olefin, with a retained geometry at the primary carbon... 

Preparation by Fries rearrangement of 4-phenylsulfonyl-phenyl acetate with alnminium chloride at 190° (52%) [2478,2479]. 

Alkyl 2-(phenylsulfonyl)[ C]acrylates Treatment of alkyl bromo[ C]acetates with sodium benzenesulfinate provides alkyl 2-(phenylsulfonyl][ C]acetates 230 (Figure 6.68). Sequential methylation, selenylation and oxidative elimination of PhSeOH coverts 230 into alkyl 2-(phenylsulfonyl)[ C]acrylates 231. powerful and versatile Michael... 

In the reaction with epoxides, y-hydroxysulfones are obtained278-280. For example, Kondo and coworkers279 synthesized various (5-lactols 226 by treating sulfone acetals 225 with terminal epoxides as shown below. Dilithiated phenylsulfonylmethylene reacted with haloepoxide and afforded 3-(phenylsulfonyl)cycloalkanols281. Treatment of y, 5-epoxysulfones 227 and 229 with n-butyllithium resulted in cyclization to form cyclopropane derivatives 228 and bicyclobutane 230, respectively282. 

If allenes bear a potential leaving group in the a-position to the cumulene system, they are very attractive substrates for palladium-catalyzed substitutions. Examples are a-allenic acetates and particularly a-allenic phosphates, which react under palladium(O) catalysis with carbanions derived from /3-diesters, /i-keto esters, a-phenylsulfonyl esters and glycine ester derivatives. They lead to /3-functionalized allenes such as 86, 89 and 93 (Eqs. 14.9-14.11) [45 18]. 

The mechanism of the aldol-Tishchenko reaction has been probed by determination of kinetics and isotope effects for formation of diol-monoester on reaction between the lithium enolate of p-(phenylsulfonyl)isobutyrophenone (LiSIBP) and two molecules of benzaldehyde. ". The results are consistent with the formation of an initial lithium aldolate (25) followed by reaction with a second aldehyde to form an acetal (26), and finally a rate-limiting intramolecular hydride transfer (Tishchenko... 

Recently, Kim and colleagues have described a new efficient method for the preparation of a-keto esters 48 via a free-radical acylation approach using (phenylsulfonyl) methoxycarbonyl oxime ether 46 as carbonyl equivalent radical acceptor (Scheme 28). The oxime 46 was conveniently prepared from readily available methylphenylsulfonyl acetate 44 by a two-step sequence (via oxime 45) as shown in Scheme 28. Nitrosation of 44 with isoamyl nitrite in the presence of sodium methoxide gave oxime 47 in 78% yield. 

The reaction of potassium dienoxy borates with A-fluorobis(phenylsulfonyl)amine (la) gives y-fluoro enones in good yield. The potassium dienoxy borates are prepared by treating potassium enolates derived from unsaturated ketones with 2-phenyl-1,3,2-benzodioxaborole. This methodology offers a convenient alternative to the traditional fluorination of dienol acetates, ethers, or enamines.145 An example is given by the formation of 13.145... 

The use of isopropylidine acetals (112) as tethers in the intramolecular Diels-Alder reactions of dienes with alkenes facilitates the formation of civ-fused cycloadducts (113) from an endo transition state (Scheme 41).218 The intramolecular Diels-Alder reaction of 4-[tris-(2-mcthylcthyl)silyl]oxy-2//-thiopyran derivatives with potential dienophiles tethered at C(2), C(3), C(5), and C(6) positions yielded cycloadducts when the dienophiles were activated with a carbomethoxy group.219 By the substitution of a phenylsulfonyl group on the dienophile of 2-benzopyran-3-ones, it is possible to enhance exo addition during intramolecular Diels-Alder cyclizations to yield a predominance of trans-fused hexaphenanthrenes related to natural products.220 The intramolecular Diels-Alder reaction of 2-furfuryl fumarates has been investigated by molecular mechanics (SIBFA)/continuum reaction field computations.221 The intramolecular 4 + 2-photo-cycloaddition of A-benzylcinnamamides (114) in the presence of C(,H6 gives 3-azatricyclo[5.2.2.01,5]undeca-8,10-dien-4-ones (115) with high stereoselectivity (Scheme 42).222... 

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