Cyclic Sulfates and Sulfites

The cyclic sulfates undergo ring opening with a wide variety of nucleophiles, such as hydride, azide, fluoride, benzoate, amines, and Grignard reagents. In some 

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The carbon atoms in cyclic sulfates and sulfites are highly reactive towards nucleophilic reagents [50], which allows us to use such functionalities as the epoxide substitutes in many reactions. The 3,5-sulfites having the neighboring free hydroxyl group were used for preparation of anhydronucleosides. Thus, D-xy/o-furanoside nucleoside 66 reacted with SOCI2 in p)Tidine to afford the cyclic sulfite 67, which upon treatment with sodium bicarbonate furnished the 2,3-anhydro-nucleoside 68 (O Scheme 21). 

The cinchona alkaloids have opened up the field of asymmetric oxidations of alkenes without the need for a functional group within the substrate to form a complex with the metal. Current methodology is limited to osmium-based oxidations. The power of the asymmetric dihydroxylation reaction is exemplified by the thousands (literally) of examples for the use of this reaction to establish stereogenic centers in target molecule synthesis. The usefulness of the AD reaction is augmented by the bountiful chemistry of cyclic sulfates and sulfites derived from the resultant 1,2-diols. 

As an alternative functional group to an epoxide, cyclic sulfates and sulfites have also been used as intermediates to prepare the taxol side chain. Thus, asymmetric dihydroxylation of cis methyl cinnamate using AD-mix (3 gave the diol 7.2.12, which was converted to the cyclic sulfate... 

Scheme 6.29 The use of cyclic sulfates and sulfites for the preparation of aziridines - ...

Cyclic sulfites (68) also are opened by nucleophiles, although they are less reactive than cyclic sulfates and require higher reaction temperatures for the opening reaction. Cyclic sulfite 77, in which the hydroxamic ester is too labile to withstand ruthenium tetroxide oxidation of the sulfite, is opened to 78 in 76% yield by reaction with lithium azide in hot DMF [82], Cyclic sulfite 79 is opened with nucleophiles such as azide ion [83] or bromide ion [84], by using elevated temperatures in polar aprotic solvents. Structures such as 80 generally are not isolated but as in the case of 80 are carried on (when X = N3) to amino alcohols [83] or (when X = Br) to maleates [84] by reduction. Yields are good and for compounds unaffected by the harsher conditions needed to achieve the displacement reaction, use of the cyclic sulfite eliminates the added step of oxidation to the sulfate. 

Chiral epoxides and vicinal diols (employed as their corresponding cyclic sulfate or sulfite esters as reactive intermediates) are extensively employed high-value intermediates in the synthesis of chiral compounds because of their ability to react with a broad variety of nucleophiles (Figs. 11.2-1 and 11.2-2). In recent years, extensive efforts have been devoted to the development of chemo-catalytic methods for their production19, 10]. Thus, the Sharpless methods allowing for the asymmetric epoxida-... 

The reactivity of cyclic sulfates and epoxides toward nucleophiles is similar. In contrast, the reactivity of a cyclic sulfite is poorer than that of cyclic sulfates or epoxides. However, with good nucleophiles, cyclic sulfites can react well at relatively higher temperature. The regio- and chemoselec-tivity of cyclic sulfites and sulfates toward nucleophiles is different from that of epoxides. For example, cyclic sulfate 62 reacts with sodium azide in acetone-water to give preferentially a-azidoester 63 (a//3 > 20 1), whereas the epoxy ester 64 gives exclusively the -substituted product 65 (/3 a > 100 1) [Eqs. (14) and (15)]. 

Scheme 3.4 Synthesis of alkyl azides from cyclic sulfates and cyclic sulfites ...

A review of cyclic sulfites and sulfates in organic synthesis includes many examples of 1,3,2-dioxathiolane 5-oxides and 5,5-dioxides <0OT7O51>. Reaction of cyclic sulfates such as... 

Oxidation of sulfite 59 using RuCh and NaI04 yielded the cyclic sulfate 60 which is now susceptible to nucleophilic attack. Treatment of 60 with NaN3 followed by acid hydrolysis of the intermediate 2-sulfate afforded the trans-i-azido-2-hydroxy derivative 61 (Scheme 3) <1997JOC4277>. 

Similar surfactants based upon glucopytanose were synthesized using the Gao and Sharpless procedure for preparation of the cyclic sulfate from methyl a-D-glucopyranoside 252 using a mixture of DMF and ethyl acetate (1 1) as solvent, the axial cyclic sulfite 253 was formed exclusively, as indicated by H NMR spectroscopy, from which the cyclic sulfate 65 was obtained in good yield (Scheme 42) <1999S621>. 

Few examples of this class of compound have been reported, although the cyclic sulfate 158 and the cyclic sulfite 159 have been reported as intermediates in carbohydrate and nucleoside synthesis, repectively <1996JOC480, 2001J(P1)1855>. 

Acidolysis of cyclic sulfites with sulfuric acid and ester interchange with dimethyl sulfate produce cyclic sulfates (104). 

The use of cyclic sulfates in synthetic applications has been limited in the past because, although cyclic sulfites are easily prepared from diols, a convenient method for oxidation of the cyclic sulfites to cyclic sulfates had not been developed. The experiments of Denmark [70] and of Lowe and co-workers [71 ] with stoichiometric ruthenium tetroxide oxidations and of Brandes and Katzenellenbogen [72a] and Gao and Sharpless [68] with catalytic ruthenium tetroxide and sodium periodate as cooxidant have led to an efficient method for this oxidation step. Examples of the conversion of several diols (67) to cyclic sulfites (68) followed by oxidation to cyclic sulfates (69) are listed in Table 6D.7. The cyclic sulfite/cyclic sulfate sequence has been applied to 1,2-, 1,3-, and 1,4-diols with equal success. Cyclic sulfates, like epoxides, are excellent electrophiles and, as a consequence of their stereoelectronic makeup, are less susceptible to the elimination reactions that usually accompany attack by nucleophiles at a secondary carbon. With the development of convenient methods for their syntheses, the reactions of cyclic sulfates have been explored, Most of the reactions have been nucleophilic displacements with opening of the cyclic sulfate ring. The variety of nucleophiles used in this way is already extensive and includes H [68], [68,73-76], F" [68,72,74], PhCOCT [68,73,74], NOJ [68], SCN [68],... 

Table 4 Reactions of 1,3,2-dioxathiolane S-oxides (cyclic sulfites) and 1,3,2-dioxathiolane S,S-dioxides (cyclic sulfates) with S-nucleophiles...

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