Osmium oxyamination

V-(p-Toluenesulphonyl)sulphilimines have been prepared under solidtliquid phase-transfer catalytic conditions from the reaction of sulphides with Chloramine-T [25] (see Section 4.5). Osmium-catalysed oxyamination of alkenes by Chloramine-T under two-phase conditions is aided by the addition of benzyltriethylammonium chloride. p-Aminoalkanols are obtained in good yields (60-75%) [26]. 

OXYAMINATION Mercury(ll) oxide-Tetrafluoroboric acid. Trioxn(/-butyl-imido)osmium (VIII). 

Nitrogen-transfer reactions of osmium imido species lead to cis diamines or amino alcohols. Reaction of 0s02(N-/-C4H9)2 [63174-13-0] with olefins produces vicinal diamines after reductive cleavage. Catalytic oxyamination of olefins using chloramine-T or AJ-chlor-AJ-argenocarbamates yields vicinal hydroxy toluenesulfonamides (112) or carbamates (113), respectively, which maybe deprotected to vicinal amino alcohols. 

OSMIUM-CATALYZED VICINAL OXYAMINATION OF OLEFINS BY CHLORAMINE-T cis-2-(p-TOLUENESULFONAMIDO)CYCLOHEXANOL AND 2-METHYL-3-(p-TOLUENESULFONAMIDO)-2-PENTANOL... 

OSMIUM-CATALYZED VICINAL OXYAMINATION OF OLEFINS BY JV-CHLORO-A-ARGENTOCARBAMATES ETHYL threo-l 1 (2-HYDROX Y-l, 2-DIPHENYI,-ETHYL)]CARBAMATE... 

This is an interesting area of osmium chemistry which stands much in need of development. Apart from the two incompletely characterized NH complexes, most of the organoimido chemistry is that of osmium(VIII) species such as Os03(NR) will undergo oxyamination reactions with alkenic double bonds, and such reactions may be made catalytic. However, because of the high reactivity of osmium(VIII), only a small range of tertiary imido complexes have been prepared (R = Bu Am , 1-adamantyl, Oct1). 

The complexes will effect oxyamination reaction with alkenes in a stereospecific reaction (Scheme 8).290 After reductive cleavage of the intermediate alkanolaminato complex (I) (see below) vicinal amino alcohols (II) are formed. The reaction is unusual in that the new C—N bond is always formed at the least substituted terminal alkenic carbon atom, and there is a clear preference for the imido complex to use its NR group for coordination to the osmium despite the steric restraints of R.299,300 However, the least sterically hindered part of the alkene moiety is attached to. the nitrogen atom.290,291,300 The yields of amino alcohols in the reaction can be improved by addition of tertiary alkyl bulkhead amines (see below). 

Oxo(/erf-alkylimido)osmium complexes are utilized in the diastereoselective oxyamination and diamination of alkenes. A mechanism involving nucleophilic attack of alkene to osmium and formation of a four-membered cyclic intermediate has been proposed38, but the [3 + 2] cycloaddition mechanism has also been suggested by quantum chemical calculations on models for hex-2-enopyranosides39. 

Oxyamination and Diamination Reactions with Imido Osmium Complexes... 

The oxyamination and diamination procedures described so far suffer from two important limitations. They require a stoichiometric quantity of osmium reagents and it is difficult to remove the tert-alkyl group from the product. Hence, procedures that employ catalytic amounts of osmium tetroxide for the preparation of vicinal hydroxy 4-methylbenzenesulfon-amides, precursors of /1-hydroxy amines, have been developed. 

Table 6. Osmium-Catalyzed Oxyamination of Alkenes with Chloramine-T...

Less than 5% enantiomeric excess was obtained in the osmium-catalyzed oxyamination of 2-phenyl-l-propene when chiral carbamates derived from 1-menthol and 1-borneol were used96, but the structures of the resulting products were not reported. 

OSMIUM-CATALYZED VICINAL OXYAMINATION OF OLEFINS BY Af-CHLORO-jV-ARGENTOCARBAMATES ETHYL fArco-[l-(2.HYDROXY-l,2-DIPHENYL-ETHYDICARBAMATE... 

An interesting offshoot of the work on osmium-catalyzed dihydroxylations is vicinal hydroxyamination [24]. Here, imido analogs of OSO4 react with olefins to produce /5-aminoalcohols by a cw-addition process. The oxyamination reaction can be made catalytic in OSO4 by employing chloramine salts of arylsulfonamides (ArS02NClNa) or carbamates. 

OXYAMINATION Mercury(II) oxide-Tetrafluoroboric acid. Trioxo(f-butyl-imido)osmium(VIII). 

OXYAMINATION Osmium tetroxide-/-Butyl-N-atgentocarbamate. Osmium tetroxide-Chloramine-T. Trioxof/-butylnitride)osmium(VIII). 

Oxyanunation. Vicinal oxyamination of olefins can be carried out with OSO4 in catalytic amounts with this N-chloro-N-argentocarbamate (c/. Osmium tetroxide-Chloramine-T, 7, 256). A major improvement over chloroamine-T is that the —COOCfCHaja group is readily eliminated. 

In an attempt to obtain garosamine (99, 3-deoxy-4-C-methyl-3-methylamino-L-ara( mo-pentopyranose) by a totally synthetic method, Dyong and Jersch reacted 4-methyl-3-penten-5-olide (97) with chloramine T-osmium tetraoxide reagent ( oxyamination reagent) and obtained the expected N-tosylaminoalcohol 98 in 50% yield. However, the next steps of the synthesis, N-methylation and... 

Sharpless oxyamination reagent, composed of chloramine-T and a catalytic quantity of osmium tetraoxide, was reacted with a series of 6-substituted 5,6-dihydro-2-methoxy-2H-pyrans. Both regioisomeric methyl 2,4-dideoxy-2-p-to-luenesulfonylamido- and 3,4-dideoxy-3-p-toluenesulfonylamido DL-/yjro-hexo-pyranosides (346 and 347) were obtained in yields of 40-60%, with the latter distinctly prevailing in mixtures. 

Vicinal oxyamination. In the presence of catalytic amounts (1%) of osmium tetroxide the trihydrate of chloramine-T reacts with alkanes to form vicinal hydroxy />-toluenesulfonamides (equation I). The effective reagent is considered to be (1). In some instances addition of silver nitrate was found to be advantageous. ... 

Oxyamination of Alkenes and Oxidation of Other Functional Groups. Osmium tetroxide catalyzes the vicinal oxyamination of alkenes to give c/s-vicinal hydroxyamides with Chloramine-T (eq 23) and alkyl Ai-chloro-M-argentocarbamate, generated in situ by the reaction of alkyl Ai-chlorosodiocarbamate (such as ethyl or f-butyl iV-chlorosodiocarbamate) with Silver(I) Nitrate (eq 24). ... 

A synthesis of the insecticidal compound allosamidine (plus isomer) and aglycone allosamizoline has been reported. The key step in the formation of the allosamizoline involved the oxyamination of cyclopentene 71 with osmium tetroxide and sodio ethyl A -chlorocarbonate in the presence of mercury(U) trifluoroacetate to afford 72 together with regioisomers. See also Chapter 19 for other syntheses of allosamizoline. 

Improved procedures for osmium-catalysed vicinal oxyamination of olefins by JV-chlorosodiocarbamates-Hg(N03)2-Et4NOAc are recommended especially for trisubstituted systems. Asymmetric induction in the reaction of OSO4 with olefins using dihydroquinidine acetate in up to 83% e.e. is now possible. "... 

Following the report last year of the first vicinal oxyamination of olefins using aminated derivatives of osmium tetroxide. Sharpless has extended this analogy to oxidations involving selenium dioxide. Two aza analogues of selenium dioxide have been prepared by either the reaction of selenium tetrachloride with the amine or... 

A new procedure for the v/c-oxyamination of olefins utilizes the trihydrate of chloramine-T and osmium tetroxide as a catalyst (Scheme 7). 

Diphenyl sulphide reacts with anhydrous chloramine-T to give an adduct (8), which is a useful reagent for the amination of olefins (Scheme 7). The osmium-catalysed oxyamination of olefins by chloramine-T has been improved by phase-transfer catalysis, and the stereospecific vicinal oxyamination of olefins by alkylimido-osmium compounds has been reported. ... 

Improvements in the osmium-catalysed hydroxylation and oxyamination of olefins continue to appear." In the vicinal hydroxylation of olefins by t-butyl hydroperoxide earlier methods involved rather alkaline conditions, but this drawback has been overcome by using Et4NOAc instead of Et4NOH and changing the solvent from t-butyl alcohol to acetone."" Although the new method works well for base-sensitive compounds (e.g. esters), it fails with tetrasubstituted olefins. Yields are generally around 70%. Vicinal hydroxy-toluene-p-sulphonamides (8),... 

---