Sulphinyl compounds

A different non-classical approach to the resolution of sulphoxides was reported by Mikolajczyk and Drabowicz269-281. It is based on the fact that sulphinyl compounds very easily form inclusion complexes with /1-cyclodextrin. Since /1-cyclodextrin as the host molecule is chiral, its inclusion complexes with racemic guest substances used in an excess are mixtures of diastereoisomers that should be formed in unequal amounts. In this way a series of alkyl phenyl, alkyl p-tolyl and alkyl benzyl sulphoxides has been resolved. However, the optical purities of the partially resolved sulphoxides do not exceed 22% after... 

In the course of this study, the authors determined /Lvalues for dibenzyl, methyl phenyl, methyl p-nitrophenyl, di-p-tolyl, di-isopropyl and tetramethylene sulphoxides and for diethyl, dipropyl and dibutyl sulphites. The /Lscales are applied to the various reactions or the spectral measurements. The /Lscales have been divided into either family-dependent (FD) types, which means two or more compounds can share the same /Lscale, family-independent (FI) types. Consequently, a variety of /Lscales are now available for various families of the bases, including 29 aldehydes and ketones, 17 carboxylic amides and ureas, 14 carboxylic acids esters, 4 acyl halides, 5 nitriles, 10 ethers, 16 phosphine oxides, 12 sulphinyl compounds, 15 pyridines and pyrimidines, 16 sp3 hybridized amines and 10 alcohols. The enthalpies of formation of the hydrogen bond of 4-fluorophenol with both sulphoxides and phosphine oxides and related derivatives fit the empirical equation 18, where the standard deviation is y = 0.983. Several averaged scales are shown in Table 1588. 

Reactions of Sulphoxides.—The general features of the reactions of sulphoxides can be illustrated by reference to the simplest structural types, without regard for stereochemical details. A minority of the new work published within the period under review falls within this category when the well-defined uses of dimethyl sulphoxide as a reagent are considered separately (p. 50), but interpretation of the reactions of sulphinyl compounds with chirality at sulphur fully in view is the outstanding feature of recent work. 

N.m.r. and i.r. spectroscopy, and chemical evidence, all suggest that the mechanism of insertion of sulphur dioxide into metal-carbon bonds in such compounds as Fe(A -C6H6)(R)(CO)2, Mo(A -C6H6)(R)(CO)3, and MnR(CO)6 involves initial formation of an O-bonded sulphinate, e.g. (23), followed by rearrangement to the stable S-bonded product, e.g. (24). The reaction of sulphur dioxide with 2-alkynyl compounds of transition metals was first considered to produce allenyl(oxy)sulphinyl compounds MS(0) 0C(R)=C=CH2. Later, the products were said to be allenyl-O-sulphinates, MOS(0) C(R)=C=CHa. Now the available evidence... 

The kinetics of the reaction between peroxomonosulphate and thiocyanate were earlier interpreted in terms of the intermediate of species such as HS(0)CN, (SCN)a, and HO(SO)CN. No definite proof of this is available, but the detection of similar intermediates, RSO2CN and R(SO)CN, in reactions between alkyl thiocyanates and peroxomonosulphate lends support to the intermediacy of HS(0)CN and HO(SO)CN in the peroxomonosulphate-thiocyanate reaction.The kinetics of decomposition of the iV-nitroso-hydroxylamine-A -sulphonate anion to sulphate and nitrous oxide have already been described under nitrogen. The mechanism of substitution at sulphur(iv) in sulphinyl compounds, RS(0)Y, is still a topic of unresolved discussion, despite much effort in this area. The question awaiting answer is whether the mechanism is simple Ssl or whether there is a four-co-ordinate intermediate of significant lifetime. > Though the determination of Bronsted coefficients did not provide definite mechanistic evidence relating to substitution at... 

E. Reaction of Aromatic Derivatives and Compounds Containing Active Hydrogen with Sulphinyl Chlorides... 

The ethylaluminium dichloride-catalyzed reaction of p-toluenesulphinyl chloride with alkenes 136 successfully applied191 for the synthesis of allylic sulphoxides 137 (equation 74) may also be regarded formally as a reaction of sulphinyl chlorides with compounds containing active hydrogen atom. Treatment of an alkene 136 with one equivalent each of ethylaluminium dichloride and p-toluenesulphinyl chloride at room temperature gave the corresponding 137. This reaction is very general and proceeds in... 

TABLE 11. /i-Chlorosulphoxides from sulphinyl chlorides, RSOC1, and unsalu-rated compounds, R CH=CH2... 

In this section alkylation, Michael additions, hydroxyalkylation (reaction with carbonyl compounds), aminoalkylation, acylation and some other reactions of a-sulphinyl carbanions will be discussed. 

Reaction of a-sulphinyl carboxylic esters 421 with carbonyl compounds has usually been performed using a Grignard reagent as a base. No condensation products are obtained using t-butyllithium or sodium hydride367,496,497 (equation 251). The condensation products formed are convenient starting materials for the synthesis of a, p-unsaturated esters and /1-ketones497. 

Addition of the dianion of /5-sulphinylcarboxylic acids to carbonyl compounds leads to the formation of the corresponding hydroxy derivatives which undergo spontaneous cyclization to give y-lactones440. Bravo and coworkers have found that when optically active ( + )-(R)-3-(p-toluenesulphinyl)propionic acid 426 is used for this reaction, the corresponding diastereoisomeric / -sulphinyl-y-lactones 427 are formed in a ratio which is dependent on the substituents in the carbonyl component441,502 503 (equation 256). 

Posner and coworkers have published a series of papers in which they described a successful application of the Michael reaction between a variety of carbanionic reagents and chiral cycloalkenone sulphoxides 557 to the synthesis of chiral organic compounds (for reviews see References 257, 649, 650). In several cases products of very high optical purity can be obtained. Subsequent removal of the sulphinyl group, serving as a chiral adjuvant, leads to optically active 3-substituted cycloalkenones 558 (equation 356 Table 27). 

The behaviour of polydentate ligands containing sulphinyl groups has received much less attention. Giesbrecht and Osorio203 have reported the coordination compounds of bivalent transition metal (Mn2+, Co2+, Ni2+, Cu2 +, Cu2+, Zn2+) perchlorates with 2,2 -sulphinyldiethanol (SDE). 

TABLE 11. /1-ChlorosuIphoxides from sulphinyl chlorides, RSOCI, and unsaturated compounds, R CH CHj... 

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