Sodium azide, reaction with epoxides

Sodium azide reacts with various epoxides at 25°-30°C at pH 6-7 to give azido alcohols [57-59]. The use of harsh conditions as earlier employed by Van der Werf et al. [59] (16-40 hr reflux in dioxane) led to the production of 1,3-diazidopropanol instead of l-azido-3-chloro-2-propanol when starting with epichlorohydrin. Several representative examples of the conditions and products of the reaction of azides with epoxides are shown in Table V. 

Reaction with epoxides. Vanderwerf and co-workers added a saturated aqueous solution of sodium azide (in slight excess) to a refluxing solution of propylene oxide in dioxane and established that the main product is l-azido-2-propanol. Cyclopentene oxide reacts to give /ran.s-2-azidocyclopentanol. 

Starting materials, like 141, which are accessible from alkenes by azido-selenenylation, afforded only in a few cases vinyl azides exclusively as shown by the example 141 142 (Scheme 5.19). In most cases, after oxidation of the vicinal phenylseleno azides and elimination reaction on the intermediate selenoxide, mixtures of allyl and vinyl azides were obtained. Ring opening of trialkylsilyl-substituted epoxides was utilized several times for stereoselective synthesis of vinyl azides. Thus, treatment of the frani -contigured oxiranes 143 with azidotrimethylsilane and boron trifluoride etherate yielded cis-conflgured products 145. This result was explained by the intermediate 144 which should undergo anti-elimination. On the other hand, when subjected to sodium azide in dimethylformamide, epoxides 146 were transformed into vinyl azides 148 via... 

The azidohydrins obtained by azide ion opening of epoxides, except for those possessing a tertiary hydroxy group, can be readily converted to azido mesylates on treatment with pyridine/methanesulfonyl chloride. Reduction and subsequent aziridine formation results upon reaction with hydrazine/ Raney nickel, lithium aluminum hydride, or sodium borohydride/cobalt(II)... 

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. 

Treatment of 51 with an excess of sodium benzoate in DMF resulted in substitution and elimination, to yield the cyclohexene derivative (228, 36%). The yield was low, but 228 was later shown to be a useful compound for synthesis of carba-oligosaccharides. <9-Deacylation of228 and successive benzylidenation and acetylation gave the alkene 229, which was oxidized with a peroxy acid to give a single epoxide (230) in 60% yield. Treatment of 230 with sodium azide and ammonium chloride in aqueous 2-methoxyeth-anol gave the azide (231,55%) as the major product this was converted into a hydroxyvalidamine derivative in the usual manner. On the other hand, an elimination reaction of the methanesulfonate of 231 with DBU in toluene gave the protected precursor (232, 87%) of 203. 

A rather complex microwave-assisted ring-opening of chiral difluorinated epoxy-cyclooctenones has been studied by Percy and coworkers (Scheme 6.131) [265]. The epoxide resisted conventional hydrolysis, but reacted smoothly in basic aqueous media (ammonia or N-methylimidazole) under microwave irradiation at 100 °C for 10 min to afford unique hemiacetals and hemiaminals in good yields. Other nitrogen nucleophiles, such as sodium azide or imidazole, failed to trigger the reaction. The reaction with sodium hydroxide led to much poorer conversion of the starting material. 

The importance of reactions with complex, metal hydrides in carbohydrate chemistry is well documented by a vast number of publications that deal mainly with reduction of carbonyl groups, N- and O-acyl functions, lactones, azides, and epoxides, as well as with reactions of sulfonic esters. With rare exceptions, lithium aluminum hydride and lithium, sodium, or potassium borohydride are the... 

Preparation of Organic Azide Compounds by the Reaction of Sodium Azide with Epoxides in Aqueous Solution [60]... 

G. Miscettaneous Nwdeopkilic Additions (1) Azide ion. The ready cleavage of ethylene oxide rings by N. ion is in acoordanoe with its recognized nucleophilic character. Alllums-Ii so far limited to three,6 8-127 -1778 publications devoted to this reaction have explored the behavior of a wide assortment of epoxides. Jt. is customary to characterize 0-azido alcohol obtained on treatmml of epoxides with aqueous sodium azide by reduction to /1-atnirm aa-o-hok.iwo. ins aa shown in Eq. (896). 

Clycidol (Eq. 898) has been treated with aqueous sodium azide or aqueous hydraaoic acid.333 Approach of the reagent occurs toward the least-substituted epoxide carbon atom in both eases. The reaction of... 

The reaction of the epoxides of cyclopentene and cyclohexene with sodium azide give the trans-azido alcohols, the hydrogenation of which affords the trans isomers of 2-aminocyclopentanol and 2-aminocyclohaexanol (eq. 9.94) stereospecifically.246 By using these reactions, Swift and Swern prepared stereochemically pure cis- and trans-1,2-diaminocyclohexanes by the reaction sequences described in Scheme 9.23.247... 

Reaction of the benzodioxocine 170 with the epoxidation reagent resulted in the epoxide 171, which was then opened with sodium azide in situ to provide trans-racemic azide 172 (Scheme 18) <2004MI265>. Reduction of the azide 172 by hydrogenolysis using Pd on carbon gave trans-racemic amine 173 in 70% yield over three steps. On acylation of the amine with acetic anhydride, the trans-racemic alcohol 174 was formed, which was then oxidized with Dess-Martin periodinane into the unstable dioxocinone 175. 

An indirect method for generating an amino alcohol (124) is to open an epoxide with azide to give the azido-alcohol 123, and subsequent reduction (19-50) gives the amine group.Sodium azide and Oxone react with epoxides to give an azi-do-alcohol. Under Mitsunobu conditions (10-17), epoxides are converted to 1,2-diazides with The reaction of trimethylsilyl azide and an epoxide was... 

The proportions of a- and /8-epoxides obtained by peracid reactions of cholest-4-ene and its 7a- and 7/3-hydroxy-, 7/8-acetoxy-, and 7-oxo-derivatives have been compared with data for similar 3-substituted cholest-5-enes. The derived 4a,5a-and 5a,6a-epoxides all reacted smoothly with sodium azide to give azido-alcohols, with maximum reaction rates when a hydroxy-group was suitably placed to provide... 

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