Vicinal oxyamination reaction

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). 

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 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). ... 

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... 

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. 

A few derivatives of taxol and of deacetylbaccatin III have been synthesized in which the dilferent hydroxyl groups have been modified for structure-activity studies these are described later in Section VII, which deals with pharmacology. However, three reactions bear special mention (a) the intramolecular cyclization of the side chain of taxol leading to the oxazolone (24) (43), (b) an approach to the functionalization of the side chain via vicinal dihydroxylation (11,46) of the cinnamate (25) to give 26, and (c) Sharpless oxyamination leading to mixtures of 2 - and 3 -oxyaminated products (see below). 

Oxyamination of olefins. This reagent reacts with a variety of olefins to give, after reductive cleavage of intermediate osmate esters, cis-vicinal amino alcohols in fair to high yield. The reaction is regiospecific in that the new C—N bond is formed at the least substituted carbon atom of the olefin. The reagent reacts more rapidly with monosubstituted olefins than with di- and trisubstituted olefins. Diols are obtained as the main products from hindered olefins. Methylene chloride or THF can be used as solvents, but pyridine is the solvent of choice. 

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