Alkene 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.2 The reagent has been used to effect hydroxyamination of alkencs with aryl amines (equation I). The rearranged isomer 1 is the major product with terminal alkenes (R3 = R4 = H). 

The same researchers found that imino derivatives of Os04 react with alkenes to produce cis-jS-amino alcohols (equation 124).346,347 This oxyamination reaction can be made catalytic in the presence of chloramine salts, e.g. ArS02NClNa or ROCONClAg.348,349... 

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). 

Recent work has shown that the carbamate reaction shows no legioselectivity in the rather demanding case of 1,2,3,6-tetrahydropyiidines 1,2-dihydropyiidines react at the 5,6 double bond, but with no selectivity in the N,0 orientation. The regioselectivities of the Sharpless oxyaminations have been rationalize, and the react on has recently been studied from the point of view of the inoiganic chemist These procedures and ther cis hydroxyaminations below produce stereochemistry complementaiy to that provided by ring Of ming of the epoxidized alkene. ... 

The oxyamination (equation 3) and diamination (equation 4) of alkenes using these imido complexes have been... 

The relative stereochemistry of the newly formed stereogenic centers attained in the aminometa-lation reaction of 1,2-disubstituted alkenes is lost if the / -aminoalkylpalladium complex is allowed to undergo /J-hydride elimination to give enamines, or if a successive reduction step is performed, unless a stereocenter is initially present in the alkene or in the amine. However, the C —Pd bond can be functionalized to achieve overall oxyamination, diamination, aziridination, aminocarbonylation, and carboamination reactions13,14. 

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. 

Most transition metal imido (nitrene) complexes are nucleophilic at nitrogen, but certain species exhibit electrophilic character. Procedures for the catalytic oxyamination and aziridination of alkenes have been developed where imidoosmium and manganese species, respectively, are generated in situ. 

The oxyamination of ( )-l-deuterio-l-decene was >95% diastereoselective. but not re-gioselective61. Complete regioselectivity was, however, observed on (E)-l-phcnyl-l-propene and 3-aryloxy-l-propene, from which l-(aryloxy)-2-hydroxypropanamides, a class of biologically active substances with -adrenergic receptor blocking effects, were obtained62. Limited reactivity of internal alkenes, especially (Z)-alkenes, was observed. Finally, phenol can be used instead of acetic acid. 

Palladium(ll)-Assisted Oxyamination of Alkenes General Procedure61 ... 

Vicinal diamines, e.g., 5, were formed as byproducts in the oxyamination of terminal alkenes with excess amine and lead tetraacetate, but were exclusively obtained when the oxidant is bromine, 3-chloroperoxybenzoic acid, or, V-bromosuccinimide64. 

Stoichiometric Oxyamination of Alkenes with terr-Butylimido(trioxo)osnuum (1) General Procedure71 ... 

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

Despite the obvious advantages the catalytic methods suffer from some limitations. A considerably lesser degree of regioselectivity was observed in the oxyamination reactions of terminal alkenes and asymmetrically disubstituted alkenes, such as 1-phenyl-1-propenes, with respect to the comparable results from stoichiometric reactions (cf. Tabic 5 and 6). Furthermore, reduced reactivity was observed, In fact, neither method (A or B) was successful with tetramethylethylene, cholesteryl acetate, diethyl ( )-2-butenedioate, 2-cyclohexenone, 1-acetoxycyclohexene or 1-phenylcyclohexene73. 

This new method of catalytic oxyamination is more effective than the chloramine-T based procedure with electron-deficient alkenes such as dimethyl ( )-2-butenedioate, but less effective with trisubstituted alkenes. However, a major advantage is that the nitrogen is now introduced bearing the more easily removed benzyloxycarbonyl and tm-butyloxycarbonyl groups. 

The, V-acyl and A- -acyloxy aziridines generated by the reaction of the corresponding azides with alkenes can be converted by heating to dihydrooxazole derivatives, so providing an overall m-oxyamination route. 

Oxyamination. The ratio of amino alcohol to diol formed by reaction of alkenes with the reagent is considerably improved by the presence of tertiary alkyl bridgehead amines. Of these ligands, quinuclidine (1, 976 4, 417) is the most efficient. In this case DME is used in place of pyridine as solvent. 

Using the simple trick devised by Seebach et ai, all nitro alcohol derivatives can be prepared dia-stereoselectively in a complementary fashion, and even p-amino alcohols, which cannot be prepared by oxyamination of alkenes, are accessible. 

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