Hydrazones sulfinylation

Enolates derived from various imino compounds have been sulfinylated in reactions analogous to those shown by equations (14) and (15). Some representative examples are shown in equations 16-18. Here again, these compounds have been utilized in asymmetric syntheses. Addition of sulfinate ester 19 to a THF suspension of a-lithio-N,N-dimethylhydrazones, derived from readily available hydrazones of aldehydes and ketones, leads to a-sulfinylhydrazones in good yield, e.g. 53 and 54 (equations 16 and 17)85,86. Compounds 53 and 54 were obtained in a 95/5 and 75/25 E/Z ratio, respectively. The epimer ratio of compound 53 was 55/45. Five other examples were reported with various E/Z and epimeric ratios. 

The reaction of 2 equiv of /V,/V-dimethylhydrazone 97, obtained by standard procedure, with 2 equiv of n-BuLi gave the corresponding a-lithioderivative, which on reaction with methanesulfinates 87 (R = Me) and 88 (R = Me) yielded o.p. sulfoxides 985 and 98R, respectively, in high yield. The configurational assignment of the a-sulfinyl hydrazone obtained was made assuming that the condensation step occurs with complete inversion of configuration at the sulfinyl sulfur, as is the case for many Andersen-type reactions. 

Little woric has been carried out on sulfmylation reactions on those systems having thiocaibonyl and imino moieties. However, hydrazones are converted to a-sulfinyl derivatives on reaction of their anions (prepared from LDA in THF) at -78 C with sulrinate esters, although the full utility of this reaction remains to be explored. Furthermore, in an unusual reaction, p-toluenesulfmyl chloride has been shown to effect a facile one-step dehydrogenation of the thiolactam (17 equation 7) in good yield. These reactions contrast with the oxidative removal of thiocarbonyl, hydrazonyl and similar functionalities with Se species (see Section 2.2.4.2). 

An acidic solution of 2,4-dinitrophenylhydrazine reacts with N-p-chlorophenyl-sulfonyl-3-ethoxy-l,2-thiazetidine 1-oxide to give (80%) the bis-2,4-dinitrophenyl-hydrazone of glyoxal. The adduct of A-sulfinyl-p-chlorophenylsulfonamide with dihydropyran is inert to catalytic hydrogenation and bromination. Treatment of two l,2-thiazetidine-3-one 1-oxides (e.g., 421) with hydriodic acid results in ring-cleavage and loss of sulfur. They are not oxidized to 1,1-dioxides by peracetic acid, ° but m-chloroperbenzoic acid accomplishes this oxidation. The unstable adducts with ketene decompose to amides with loss of hydrogen sulfide and sulfur dioxide or may be trapped by reaction with aromatic amines as shown for thiazetidine 1-oxide 422.An aldol-type condensation has been reported for A -cyclohexyl-1,2 thiazetidine-3-one 1-oxide and p-(A(A"-dimethylamino)benz-aldehyde. " Sulfur monoxide is lost in the flash-vacuum thermolysis of 422a. ... 

Aldol-type condensation of chiral a-sulfinyl hydrazones with aldehydes also provides a route leading to chiral 3-hydroxy ketones. - This is exemplified by the synthesis of (-)-(/ )-[6]-gingerol (98 equation 24). ... 

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