Allyl sulfoxide anions synthesis

Hua has used the products of Pauson-Khand cycloadditions for syntheses of optically active pental-enene and racemic pentalenolactone E methyl ester. The racemic ketone in the first case was converted to the necessary optically active intermediate by kinetic resolution via 1,4-addition of an optically active allyl sulfoxide anion. These represented the first synthesis of natural products containing the angularly fused triquinane skeleton from bicyclic Pauson-Khand products (equation 53 and Scheme 20). ... 

Evans, D. A., Andrews, G. C., Fujimoto, T. T., Wells, D. Application of allylic sulfoxide anions as vinyl anion equivalents. General synthesis of allylic alcohols. Tetrahedron Lett. 1973, 1385-1388. 

A close relative of the previous tandem [3,3]-[3,3] sigmatropic rearrangement invokes its tandem [2,3H2,3] counterpart the allylic sulfoxide-sulfenate rearrangement. As a key step in the synthesis of 5-deoxyleukotriene D, Corey applied the sequence of transformations illustrated in Scheme 12. The anion of allylic sulfoxide (149) undergoes 1,2-addition to methyl 5-formylpentanoate followed by low temperature benzoylation. Upon wanning the reaction mixture to ambient temperature, a facile sulfox-... 

Anion (63), prepared from an allyl sulfoxide and LDA, reacts with alkyl halides at the a-position to give a-alkylat sulfoxides, which undergo rearrangement upon treatment with a thiophile, resulting in formation of allylic alcohols (Scheme 37). This method can be applied to the synthesis of cyclic allylic alcohols (Scheme 38). The reaction of (63) with aldehydes produces a mixture of regioisomers and thus it is less synthetically useful. 

Enhancing the utility of the allq lation-rearrangenient sequence in synthesis, the Evans group addressed the problems of a-versus-y alkylation as well as low anion reactivity by employing heterocyclic sulfides as the alleviation substrates tScheme IR.IfiE For instance, allylic imidazolyl sulfide 56 could be allqvlated efficiently, reaction at the a-position being favored by a chelated but reactive allyl lithium intermediate. Oxidation of 57 to the allylic sulfoxide and treatment with a secondary amine thiophile provided allylic alcohol 58 in high yield and with excellent stereoselectivity at the trisubstituted alkene. Allylic oxidation with manganese dioxide completed a synthesis of the sesquiterpene nuciferal (59). ... 

Sulfur Chemistry - Two facile methods of the heretofore difficult sulfoxide to sulfide reduction have been accomplished with dilsobutyl aluminum hydride and dichloroborane in THF at 0 . With the latter reagent, ketones, esters, and amides remain unaffected. A review on sulfoximes and derivatives as synthetic reagents presents some new methods for the preparation of various oxiranes, aziridines, alcohols, cyclopropanes, and alkenesAllylic sulfoxide anions have proven useful for the synthesis of ally lie alcohols, including trisubstltuted olefinic allylic alcohols. Transesterification between a dialkylacylphosphonate and a sulfonic acid yields sulfonate esters. The oxidation of aliphatic mercaptans to sul-finio acids with the use of m-chloroperbenzoic acid is especially useful in that the excess perbenzolc acid is removed by precipitation at -80. ... 

The Pd-catalyzed allylic alkylation strategy was also applied to the synthesis of allyl sulfoxides 318 by Poli et al. The use of sulfenate anions 319 (Scheme 46.37), generated from 3-sullinylesters 317 by a retro-Michael reaction under biphasic conditions, is noteworthy. 

The alkylation of sulfur-stabilized anions has been the subject of an excellent recent review633. Anions adjacent to a wide range of sulfur functionalities may be alkylated readily, the most common being sulfoxide and sulfone a-anions. In the synthesis of retinoic acid derivatives and vitamin A634-636, a-sulfonyl anions have been alkylated with an co-acetoxy-containing allyl halide in good yield (equation 96). 

Madec and Poli recently reported that sulfenate anions can also be used as nucleophiles in catalytic formation of C ryi-S bonds, generating sulfoxides [103]. The sulfenate anions are generated in situ by base-induced elimination of (3-sulfinyles-ters [136]. These groups subsequently developed an enantioselective variant, allowing the asymmetric synthesis of sulfoxides with up to 83% ee (16) [105]. Chiral sulfoxides are present in a variety of pharmaceuticals and are widely used in asymmetric catalysis [137-141]. Likewise, Madec and Poli found that sulfenate anions can be used to generate Csp -S bonds in Pd-catalyzed allylic alkylation [ 142]. o... 

As Evans pointed out, from a synthesis strategy point of view, regioselective alkylation of a sulfoxide-stabilized allylic anion (120 121 Scheme 1R.34T followed by [2,31-... 

Mori was clearly intrigued by juvabione. Nearly 25 years after his first synthesis, his group described the third conjugate addition approach we will consider. This synthesis addresses both relative and absolute stereochemistry problems. The plan was to prepare the anion derived from vinyl sulfoxide 149 and examine its reaction with cyclohexenone (127). There was precedence for the 7-carbon of this type of allylic anion to behave as the nucleophile in conjugate additions (Hua). The hope was that this addition would take place with good diastereoselectivity and that the sulfoxide would influence the absolute stereochemistry of the process. 

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