0-Sultines

Cleavage of the oxathiane moiety can be carried out with iV-chlorosuccinimide/silver nitrate and leads to the a-hydroxy aldehyde 21 along with a diastereomeric mixture of sultines 20. The sultines can be reduced to the hydroxy thiol 22 which can be reconverted to the chiral auxiliary 16 in ail overall recovery of about 70%39. 

Molecular rearrangements such as that of Stevens248,265 or the sulfoxide - sulfinic acid, Ramberg-Backlund15 or sultone -> sultine rearrangements, are quite common in these classes of compounds. 

Braverman and Reisman111 have found that addition of a carbon tetrachloride solution of bromine to bis-y,y-dimethylallenyl sulfone 20 at room temperature unexpectedly resulted in spontaneous and quantitative fragmentation of the sulfone, with formation of the cyclic a, /3-unsaturated sulfmate (y-sultine) 43a and the tribromo products 44 and 45 (equation 38). Analogously, treatment of the same sulfone with trifluoroacetic acid gives rise to y-sultine 43b. It is interesting to note that from a synthetic point of view it is not even necessary to prepare the diallenyl sulfone 20, since one can use its sulfinate precursor (equation 24) to obtain exactly the same results, under the same conditions. The authors suggested that the fragmentation-cyclization of sulfone 20 may take place by the mechanism depicted in equation 39. 

All the y-sultines were obtained as diastereomeric mixtures (ca 1 1, by NMR), and each one of y-sultines ( + )-49 and ( + )-51 (R = t-Bu) was separated into two diastereomers A and B by column chromatography. The oxidation of y-sultines (— )-49A and (+ )-49B to the corresponding optically active sultones (+ )-52A,B, which lack a chiral sulfur, may be taken as proof that the observed optical activity in the sultines is also due to the y-carbon. This result seems to exclude the intermediacy of vinylsulfene in the reaction mechanism, since its disrotatory closure would lead to racemic y-carbon in the product. 

The identity in sign and similarity in optical rotations of sultones (+)-52A,B, obtained from (—)-49A and (+)-49B, indicate that the absolute configuration of the y-carbon in both sultones as well as in both sultines is the same. In conclusion, the authors suggested113,114 that of the four possibilities shown below, y-sultines 48A-51A and 48B-51B may be assigned the (R)c-(Sf and (R)c-(Rf absolute configurations, respectively. Although initiated by mechanistic interest, this study has also resulted in a new method for selective synthesis of... 

In the analogous studies of the photolysis of sulfolane (31), the work of Honda and coworkers66 was carried out in the gas phase at 70-130 °C and established the formation of S02, ethylene, cyclobutane and acetylene as the major products, on mercury-sensitized photolysis. In considerable contrast, photolysis of sulfolane at 185 nm in the liquid phase67 produced ethylene( = 0.22), the sultine (32) (parallel experiments on aqueous solutions of sulfolane, a sulfinic acid is also believed to be formed. The authors believe that both four-membered (33) and six-membered (32) sultines may be formed during these photolyses. Further work in this area would appear to be necessary to unravel the full mechanistic details. 

When the ring system containing the sulfone moiety is unsaturated, a quite different set of products has been observed on photolysis, apparently arising from an initial cycloreversion to a short-lived sulfene intermediate. For example, irradiation of 2H-1-benzothiopyran 1,1-dioxide (41) in dichloromethane or methanol gave the cis- and trans-sultines (42) and the ring-expanded sultine (43) in roughly equal amounts, accompanied by minor amounts ( 5%) of the products of formal loss of S02, i.e. indene, and SO, i.e. 4472... 

Sulphuranes - see also Dialkoxysulphuranes, Oxysulphuranes as intermediates 406 Sulphur bonding 484-493 Sulphur-containing groups, stereoelectronic effects of 584-594 Sulphur dioxide addition to 215-217 extrusion of 137, 140, 141, 158, 163, 397-402, 801, 805, 962, 1098 Sulphur monoxide, extrusion of 397-402 Sulphur trioxide, reactions of 217, 218 Sultenes, as intermediates 743 Sultines 679, 943 as photolytic products 881, 882... 

The formation of cyclic sulfinic esters (sultines) from vinyl sulfenes is known , and the trapping of the expected intermediate vinyl sulfene in the thermolysis of thiete dioxide (6fc and 194) has been convincingly achieved . Specifically, thermolysis of thiete dioxide 6b in the presence of norbornenes gave cycloadducts of the Diels-Alder type (i.e. 252b), resulting from the trapping of the vinyl sulfene formed. The accumulated evidence thus supports the proposed mechanism for these thermolytic reactions. 

In contrast with the relatively facile thermal rearrangement of sulfinates to sulfones discussed in the preceding section, the reverse process is relatively, rarely encountered and is usually observed only at elevated temperatures. One of the first thermal sulfone to sulfinate isomerizations has been invoked by Fields and Meyerson to occur during the pyrolysis of dibenzothiophene S, S-dioxide (26) to dibenzofuran, through elimination of sulfur monoxide from the sultine intermediate 27 (equation 27). More recently, the flash vapor-phase pyrolysis of various 2,5-dialkyl and diaryl thiophene-S, S-dioxides has also been shown to involve SO extrusion and formation of the corresponding furans in good yields . 

Rearrangements involving sulfones chiral a,j -unsaturated y-sultines. 

Despite the aversion of the sulphonyl group to function as a nucleophile, there are a limited number of literature reports that deseribe sueh a process . The first of these does not lead to a reduetion at sulphur and is thus not direetly relevant, but the report by Braverman and Duar deseribes reaetions in whieh an acetylenie sulphinate ester ean undergo a [2,3] sigmatropie rearrangement to an allenie t-butyl sulphone. Reaetion of this sulphone with the appropriate eleetrophile, for example bromine, gave a y-sultine, formation of whieh requires the partieipation of the sulphonyl group in an intramoleeular cyclization process. The reactions are outlined in equation (40). 

Very limited information is available through direct enzyme studies for DszA. However, its specificity for couple of possible intermediates resulting from DszC reaction has been studied. The DszA enzyme was capable of converting dibenz[c,e][l,2]oxanthiin 6,6-dioxide (sultone) as well as sultine to 2,2 dihydoxybiphenyl (DHBP), in addition to its inherent activity towards DBT sulfone. However, the relative activities were lower than the activity towards DBT sulfone (54% and 23%, respectively). The proposed pathway for this reaction is given in Fig. 2 [26,153],... 

The mechanism and synthetic scope of reactions of monohaptopropargyl-iron complexes has been described earlier (see Schemes 30-33 in Section IV,A,2). By using sulfur dioxide and sulfur trioxide as electrophilic reagents, it is possible to synthesize metal-containing heterocycles in the reduced 1,2-oxathiole category (sultines and sultones) (Scheme 119).182-184 An... 

Langa et al. [67] described the microwave-induced Diels-Alder reaction of o-quino-dimethane, generated in situ from 4,5-benzo-3,6-dihydro-l,2-oxathiin-2-oxide (74) (sultine), [68, 69] leading to cycloadduct 75 (Scheme 9.21). This reaction was the first application of microwave irradiation to the preparation of a functionalized C60 [67]. 

Durst and his associates have examined the interesting behavior of / -sultines, which are themselves formed when /-butyl / -hydroxysulfoxides are treated with various chlorinating agents (Durst and Gimbarzevsky, 1975 Jung et al., 1973). Earlier work by Corey and Durst (1966) had revealed some mechanistically interesting behavior of /Miydroxy- and / -ketosulfmamides. 

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