A-Phosphoryl sulfoxide

An a-phosphoryl sulfoxide (4) has also been prepared by the reaction of the appropriate carbanion with sulfinate ester 19 (see also Section II.A.l)18. Ugi and coworkers prepared (S, R, S)-65 by reaction of (R, R)-64 with ester 19. The (S, S, R) diastereomer was prepared from (S, S)-6496. 

It is of interest to note that the magnetic nonequivalence of the enantiomers of the a-phosphoryl sulfoxide 49 in the presence of TFMC was observed (88) not only in Hbut also in and NMR spectra. With regard to the accuracy of the NMR method, the P H NMR spectra proved very useful in this case, since only two well-separated singlets that were due to enantiomeric sulfoxides 49 were observed. 

A similar extent of asymmetric induction was observed (88) in the Pummerer reaction of optically active a-phosphoryl sulfoxide 49, which results in the formation of the corresponding optically active a-acetoxy a-phosphorylmethyl sulfide 277. 

In the course of further studies it was found (302) that the Pummerer reaction of a-phosphoryl sulfoxide 49 catalyzed by bromine or carried out in the presence of dicyclohexylcarbodiimide... 

Chiral vinyl sulfoxides can also be prepared Horner-Emmons reaction of carbonyl compounds with a-phosphoryl sulfoxides which are obtained from lithiated dimethyl methylphosphonate and (-)-menthyl (S)-p-toluenesulfinate (eq 8). However, this reaction applied to carbonyl compounds often gives a mixture of the (E) and (Z) isomers of the vinylic sulfoxide. 

The reaction of a-phosphoryl sulfoxide with the dimethyl acetal of pyruvic aldehyde allowed the preparation of the corresponding vinylic sulfoxide as a 1 1 mixture of (E) and (2) isomers which could be isomerized with Lithium Diisopropylamide to the lithiated (E) isomer, used for the asymmetric synthesis of a-tocopherol (eq 9). ... 

The course of the alkaline hydrolysis of (diphenoxyphosphonyl) p-tolyl sulfoxide (345) has been elucidated utilising isotopic labelling and mass spec-trometric analysis of the hydrolysis products. The results obtained do not support a two-step mechanism for the hydrolysis of a-phosphoryl sulfoxides instead there is participation of the neighbouring sulfinyl group and formation of a cyclic oxathiaphosphetane intermediate. ... 

Mikolajczyk, M., Zatorski, A., Grzejszczak, S., Costisella, B., and Midura, W., a-Phosphoryl sulfoxides. Part 4. Pummerer rearrangements of a-phosphoryl sulfoxides and asymmetric induction in the tt ansfer of chirality from sulfur to carbon, J. Org. Chem., 43, 2518, 1978. 

Mikolajczyk, M., Midura, W.H., Grzejszczak, S., Montanari, E, Cinquini, M., Wieczorek, M.W., and Karolak-Wojciechowska, J., a-Phosphoryl sulfoxides. Part 8. Stereochemistry of a-chlorination of a-phosphoryl sulfoxides, Tetrahedron, 50, 8053, 1994. 

Phase-transfer catalysis. A Polish group reported that the Wittig-Horner reaction with a-phosphoryl sulfoxides, sulfones, and sulfides could be conducted in a two-phase system (aqueous NaOH-methylene chloride) with benzyltriethyl-ammonium chloride as catalyst. Later work showed that a catalyst was not necessary because these sulfur compounds themselves can function as catalysts for phase-transfer reactions. Thus (1) is an effective catalyst for alkylation of ketones by alkyl halides in the presence of 50% aqueous NaOH. Related, but somewhat less active, catalysts are sulfones such as (2), a-disulfoxides (3), and bisphosphonates (4). 

Dienes, as the simplest polyene systems, are widely encountered in sex pheromones like (4E, 7Z)-4,7-tridecadienyl acetate (100), a component of the sex pheromone of the potato tuberworm moth (Phthorimaea operculella). This compund was synthesized by Kim and Park [54] starting from a protected 5-hexen-l-ol and utilizing the chemistry of thio-substituted phosphonates (Scheme 28). Thus, the Pummerer rearrangement of a-phosphoryl sulfoxide 101 with 5-hexenyl acetate 102 afforded 7-acetoxy-l-methylthiohept-3-enyl phos-phonate 103 as an E/Z=85 15 mixture, being unreactive in the Horner-Wittig reaction, even after OAc deprotection/THP reprotection. However, the reaction of the more reactive a-phosphoryl sulfone 104 with w-hexanal successfully led to the required 1,4-diene 105, as an ElZ = 70 30 mixture, in 86 % yield. The final pheromone 100 was obtained after the desulfonylation of 105 with sodium hydrosulfite and the OTHP OH OAc deprotection/reprotection procedures. 

The synthesis of racemic oc,P-unsaturated sulfoxides by the Homer-Wittig olefination of aldehydes is a well-established process [15]. In this procedure, deprotonation of a dialkyl arenesulfinylmethanephosphonate and reaction of the resulting anionic species with an aldehyde gives oc,P-unsaturated sulfoxides in high yield, but with variable (E) (Z) ratios according to the nature of the aldehyde. For example, reaction of a-phosphoryl sulfoxide (7) with benzaldehyde (8) gives the ct,P-unsaturated sulfoxide (9) in 70% yield with an ( ) (Z) ratio of 58 42 (Scheme 5.3) [16]. 

The first report concerning the synthesis of enantiomerically pure dienyl sulfoxides was made by Hoffmann and coworkers [32], who made use of the Horner-Wittig reaction between an a-phosphoryl sulfoxide and acrolein to give the corresponding dienyl sulfoxides as a mixture of geometric isomers. Recently, there has been considerable interest in the synthesis of 1-sulfinyl and 2-sulfinyl-l,3-butadienes, as these types of substrates have considerable potential as diene components in asymmetric Diels-Alder cycloadditions. 

In light of the observation that Wittig-Horner-Emmons reactions require no additional catalyst [6] and that certain a-phosphoryl sulfoxides catalyze basic two-phase alkylations [7], it is clear that more study is required. The alkylation of several carboxylate anions are recorded in Table 6.1. 

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