Sulfinimines oxidation reactions

Oxidation of 3-amino-1,2-benzisothiazoles 20 using nitric acid was reported to give 21 in 48% yield 27 On the other hand, oxidation of benzisothiazole 22 with m-CPBA afforded sulfinimine 23 which showed significant in vivo antipsychotic activity.9 The latter reaction was run at -78 °C in methylene chloride to minimize overoxidation. Inferior results were obtained when nitric acid was used as the oxidant. 

The availability of f j-di-r-butyl disulfide monoxide from selective oxidation catalyzed by vanadyl-88 enables the preparation of chiral r-butyl sulfinamides, sulfoxides, and sulfinimines. Very similar reaction conditions bring about the transformation of various 1,3-dithianes to chiral monoxides. (/ ,Rl-2,2,5,5-Tetramethyl-3,4-hexanediol is a chiral ligand for the Ti(IV)-catalyzed oxidation of sulfides with cumene hydroperoxide. ... 

Substituted 2-oxazolidones 165 are useful chiral auxiliaries for diastereoselective functionalization at the a-carbon of their amide carbonyl group. The a-fluoroaldehydes 166 were prepared by a series of reactions electrophilic fluorination of the corresponding oxazolidinone sodium enolates with AMluorobenzenesulfonimine reductive removal of the auxiliary with LiBH4 and Dess-Martin oxidation. The aldehydes are so unstable for isolation that they are converted with (R)-/ -toluenesulfinamide to /7-toluenesul(inimines 167, which are isol-able and satisfactorily enantio-enriched. Chiral sulfinimine-mediated diastereoselective Strecker cyanation with aluminum cyanide provided cyanides 168 in excellent diastereose-lectivity, which were finally derived to 3-fluoroamino acids 169 (see Scheme 9.37) [63]. 

Sulfenimines undergo asymmetric oxidations to form sulfinimines via a reaction with Davis reagents. The sulfenimine 77 was oxidized by 9 to yield the sulfmimine 78 in 82% yield and 97% ee. Yields and enantiomeric excess varied based on the oxaziridine reagent used.64... 

Enantiopure sulfinimines (thiooxime-S-oxides) 44 have been reported to facilitate the asymmetric Strecker reaction.28 Davis found that typical cyanide sources, such as potassium cyanide and TMSCN, did not possess sufficient reactivity for addition to the sulfinimines. Product 46, however, could be obtained using the more Lewis acidic Et2AlCN. Not only did the coordination of the aluminum to the oxygen of the sulfinimine activate the imine toward nucleophilic addition, this complexation also facilitated the delivery of the nitrile (see 45), These results triggered numerous modifications and variations that have enhanced this approach to chiral a-amino acids. 

Scheme 1034. The synthesis of (l/ )-l-phenylpropylamine hydrochloride. Beginning with tert-butyl disnlfide, oxidation with hydrogen peroxide in the presence of VO(acac>2 and (5 )-2-(A -3,5-di-f-butylsaIicylidene)amino-3,3-dimethyl-l-butanol prodnces the chiral sulfinate (5 )-f-butyl-f-butanethiosulfinate. Then, addition of the sulfinate in THF (oxocyclopentane, THF) to a suspension of lithium amide (L1NH2) in Uquid ammonia (NHs )) generates K)-t-butanesulfinamide. The optically active sulfinamide reacts with propanal to form the corresponding sulfinimine. Reaction of the latter with phenylmagnesium bromide (CtllsMgBr) in ether yields A -(l-phenylpropyl)-f-butanesulhnamide and hydrolysis in methanolic HCI generates the corresponding (IR)-l-phenylpropylamine hydrochloride. The cartoon drawing of the presumed cyclic transition state is used to account for the stereochemical outcome. But see Hose, D. R. I Mahon, M. E Molloy, K. C. Raynham, T Wills, M. /. Chem. Soc. Perkin Trans. 7,1996, 7, 691.

---