Alcohols 3-azido, from epoxides

Scheme 8.11. (a) Group-selective ring-opening of meso epoxides by nucleophiles leads to enantioselective syntheses of 1,2-difunctionalized compounds, (b) Azido alcohol synthesis from epoxides and trimethylsilyl azide as catalyzed by (salen)CrCl complexes (see Scheme 8.6a for general structures of salen catalysts)... 

Synthesis of azindines from epoxides via amino alcohols or azido alcohols and reaction with phosphines or phosphites... 

As described above, 1,2-azido alcohols can be stereospecifically prepared from epoxides. 1,2-Azido alcohols thus prepared reacted with triphenylphosphine or trialkyl phosphites to afford aziridines, where inversion of both centers of the original epoxides takes place (Scheme Intramolecular oxirane... 

A mixture of the epoxide ca. 5 mmol), sodium azide (6 g, activated by the method of Smith) and 0.25 ml of concentrated sulfuric acid in 70 ml of dimethyl sulfoxide is heated in a flask fitted with a reflux condenser and a drierite tube on a steam bath for 30-40 hr. (Caution carry out reaction in a hood.) The dark reaction mixture is poured into 500 ml of ice water and the product may be filtered, if solid, and washed well with water or extracted with ether and washed with sodium bicarbonate and the water. The crude azido alcohols are usually recrystallized from methanol. 

The addition of iodine azide to primary allylic alcohols occurred with complete regio- and simple diastereoselectivity allowing the direct preparation of valuable 3-azido-1,2-epoxides, e.g., 12 and 13, by base-promoted elimination of hydrogen iodide from the intermediate 3-azido-2-iodo alcohols44. 

Epoxy alcohols react with Et2AlN3 under mild reaction conditions to afford 3-azido-l,2-diols resulting from the regio- and stereoselective attack of the nucleophile at the C-3 carbon of the epoxides [121]. Here the high regioselectivity observed with both cis- and trans-substituted epoxides is not affected by bulky substituents at C-3 (Sch. 85). 

In the presence of a palladium catalyst, allyl epoxides (113) react with nitrogen nucleophiles at the al-kenic carbon atom remote from the oxirane ring to give 1,4-adducts (114)." In the absence of a palladium catalyst, azide ion attacks the oxirane ring affording 1,2-adducts (115 Scheme 52 and Table 2)." Vinyl epoxide (116) gave 1,2- and 1,4-azido alcohol in a ratio of 1 1.5 irrespective of the reaction system. " Intramolecular cyclization of vinyl epoxide (117) in the presence of a palladium catalyst afforded isoquinuclidine (118 Scheme 52). ... 

When racemic aryl glycidyl ethers were subjected to aminolysis in aqueous buffer catalyzed by hepatic microsomal epoxide hydrolase from rat, the corresponding (S)-configurated amino-alcohols were obtained in 51-88% ee 131. On the other hand, when azide was employed as nucleophile for the asymmetric opening of 2-methyl-1,2-epoxyheptane in the presence of an immobilized crude enzyme preparation derived from Rhodococcus sp., which contains an epoxide hydrolase activity, the reaction revealed a complex picture 1321. The (S)-epoxide from the racemate was hydrolyzed (as in the absence of azide), and the less readily accepted (i )-enantiomer was transformed into the corresponding azido-alcohol (ee >60%). Although at present only speculations can be made about the actual mechanism of both the aminolysis and azidolysis reaction, in both cases it was proven that the reaction was catalyzed by a protein and that no reaction was observed in the absence of biocatalyst... 

The synthesis begins with the preparation of epoxide 12b from shikimic acid as described in the literature [47]. Nucleophilic ring opening of MOM-protected epoxide 12c with sodium azide in the presence of ammonium chloride generates azido alcohol 12d. The ring opening of the epoxide is... 

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