Azides 5-hydroxy

These reactions are especially favorable for [T and y-hydroxy azides, where reaction can proceed through a hemiketal intermediate. 

Pearson et al. (40) observed an unprecedented low-temperature [3 + 2] or [3 + 3] cycloaddition of azides with allylic carbocations, yielding triazolines or dihydro-triazolines (Scheme 9.40). When the hydroxy azide 182 was treated with SnC at —78 °C, a diastereomeric mixture of crystalline triazohnes 183 was obtained. A... 

Cleavage of epoxides The epoxide 1 is cleaved by N3Si(CH3)3 and a catalytic amount of ZnCl2 to the hydroxy azide 2 in 90% yield. The corresponding benzoate (3) on hydrogenation undergoes O — N benzoyl transfer to provide 4 in 95% ee. 

Chiral a-hydroxy RSMAs are obtained from a-chiral silyl epoxides by classical trans addition of sodium azide followed by reduction of the intermediate a-hydroxy azide (see Section III.A.7).311... 

Vinyl azides have been prepared by treating epoxides (78) with azide ion to give azido alcohols (79) which are then dehydrated to the vinyl azide.30 This method also complements the iodine azide method since the epoxide route usually gives the isomeric vinyl azide. -Hydroxy azides (81) can also be prepared by the sodium borohydride reduction of a-azidoketones (80). 

The epoxide is one diastereoisomer (trans) but racemic and the symbol ( ) under each structure reminds you of this (Chapter 15). Azide attacks at either end of the three-membered ring (the two ends are the same) to give the hydroxy-azide. The reaction is carried out in a mixture of water and an organic solvent with ammonium chloride as buffer to provide a proton for the intermediate. 

Lonthonum Triazide, La(N5), mw 222.97, N37.25JJ, Curtius and Darapsky prepd the basic salt. Lanthanum Hydroxy azide. La (OH)(Nj), l/ H,0, by boiling a soln of lanthanum nitrate and sodium azide. The white slimy mass of basic lanthanum azide was obtained either on evapg the mixed soln in vacuo or on treating it with a mixt of ale eth. No props of the product were reported nor were there any addnl refs found in which any attempts were made to prepare and isolate the lanthanum azide... 

J-Hydroxy Azides, 1,2-Diazides and a-Azido Ketones From Steroid Alkenes... 

Publications in 1951 and 1954 utilized this characteristic absorption at ca. 2100 cm" to demonstrate the structure of a )8-keto azide and an a-hydroxy azide, respectively. The assumption that other functional groups in the molecule did not interfere was justified by a report in which both alkyl and aryl azides were studied, followed by a paper dealing with a-substitution. The clear result of all of this was the constancy of the azide asymmetric stretching frequency. Sheinker and co-workers have made similar studies and report the interesting conclusion that the intensity of the band is more sensitive to structure than is the position of the band. The intensity is raised by electron donor groups and lowered by substitution of electron acceptor groups. 

Oxazole derivatives can also be obtained from azides by reactions which involve acidolysis. jS-Hydroxy azides react with aromatic aldehydes in sulphuric acid, thus 2-azidoethanol and bcnzaldehyde yielded (71%) 2-phenyl-A -oxazoIine (202) . 

Epoxide-opening with sodium azide and a weakly acidic catalyst is increasingly used as a route to hydroxy-azides, and thence to hydroxy-amines [e.g. 16a, 17a-epoxyandrostane — 16 -azido-17a-ol" " 6o,7a-epoxy-4-en-3-one — 6 -azido-... 

Rearrangement of the initially formed hydroxy-azide (81) gave the D-homo-16jS-azidoketol (82), when a 16a,17a-epoxypregnan-20-one (80) was treated with sodium azide and sulphuric acid. [Assuming the D-homoannulation to be... 

A new method for the preparation of hydroxyamines, e.g. (317), from 17-ketones which provides a route to D-homo-androstanes in high yield has been devised. Methylenation of the 17-ketones with dimethylsulphonium methylide or dimethyl-sulphoxonium methylide affords, in almost quantitative yield, (and stereo-selectively in the case of the former reagent) the oxirans (315) which are readily converted into hydroxy-azides (316). 

To avoid decomposition of the sensitive 2-hydroxy azide side chain with Lewis acid, the azide functional group was reduced to amine. These conditions also deprotected the carboxy terminus. After TBS deprotection in acidic conditions, the 2-amino alcohol was treated with excess BBtj for deprotection of Cbz (benzyloxycarbonyl) and OMe groups. Synthesis of biphenomycin B 53 was completed in 14 steps affording 15% overall isolated yield. 

The radical fragmentation of )5-hydroxy azides has been investigated by Suarez. For example, treatment of an azidoalcohol derived from Umonene with diacetoxyiodobenzene... 

Hydrazoic acid may be added to activated olefinic bonds to yield azides. Some epoxy compounds have also been reacted with sodium azide to form hydroxy azides. 

Hernandez, R., Leon, E.I., Moreno, P., and Suarez, E, Radical fragmentation of P-hydroxy azides. Synthesis of chiral nitriles,/. Org. Chem., 62, 8974, 1997. 

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