Triphenylphosphine, reduction azides

Scheme 7. Preparation of pyrazine dimers using triphenylphosphine for azide reduction.

Azido-5 -deoxy-nucleosides auid 5 -azido-2, 5 -dideoxy nucleosides have been prepared by a polymer support method, using polystyrenesulphonyl chloride reagent in conjunction with lithium azide,which on triphenylphosphine reduction yielded the corresponding amino-sugar nucleosides. ... 

The reduction of an azide group with triphenylphosphine in tetrahydrofuran by microwave heating at 130 °C for 5 min has been described by Kihlberg and colleagues (Scheme 6.152) [297]. The use of diethyl 4-(hydrazinosulfonyl)benzyl phosphonate as an in situ diazene precursor for the reduction of trisubstituted gem-diiodoalkenes to terminal geminal diodides under microwave conditions has also been reported [298],... 

Scheme 6.152 Reduction of an azide group with triphenylphosphine.

One of the classical methods for the synthesis of pyrazines involves dimerization of an a-amino carbonyl compound and subsequent aromatization. Cyclic dimerization of the a-amino ketone, which is formed by reduction of a-azido ketone 149 with triphenylphosphine, leads to the formation of a pyrazine derivative 150 (Scheme 40) <1994JOC6828>. Reduced Te also dimerized a-keto azide 149 to give pyrazine 150 <2006JOG2797>. 

Potassium bisulfite reduces fluoroalkylnitroso compounds to the oximes, with the exception that the parent mtrosotnfluoromethane is converted to the corresponding hydroxylamine [90] (equation 72). ArylfluoroaJkylazo compounds are reduced to the hydrazo stage or the fluoroamine by zinc-add, depending on conditions [91] (equation 73) Of the various reagents tested tor selective reduction of ji-fluoroalkyl azides to P-fluoroalkylamines, triphenylphosphine was the best [92] (equation 74). 

By far the most common method of formation of IMPs is the Staudinger reaction.1 This is the reduction of an organic azide with triphenylphosphine (Scheme 4). It has been proven that attack of the phosphorus is at the terminal nitrogen of... 

The first protocol describes the simple reduction of an organic azide employing triphenylphosphine and water in tetrahydrofuran... 

With a clever modification of conditions it is possible to desymmetrize a diazide. This is achieved by selective reduction of one of the azide moieties. As soon as the reduction of the first azide has occurred, the resultant amine is pro-tonated and carried into the phosphoric acid layer, preventing further interaction with triphenylphosphine. 

Protocol 3 is an example of an aza-Wittig reaction using l,2-bis(diphenyl-phosphino)ethane (DPPE or DIPHOS). The IMP is generated by reduction of the azide by DPPE, intramolecular reaction with the aldehyde group then occurs. It is worth noting the replacement of triphenylphosphine with DPPE. In the reaction... 

Azides are converted into amines by the Staudinger reaction. It is a very mild azide reduction with triphenylphosphine. ... 

In the first step a Staudinger reduction of the azide to the amine takes place, wherein triphenylphosphine reacts with the azide and forms a phosphazide, which then loses N2 and forms the iminophosphorane. Aqueous workup then generates the amine with phosphine oxide as a side product. The amine formed then undergoes macrolactonization to 63 with loss of acetone. 

Conversion of azido group in 13q to acetamido derivative 13r has been efficiently accomplished in 68% yield via a two-step sequence reduction of the azide functionality with triphenylphosphine in tetrahydrofuran and acetylation of the amine with acetyl chloride. 

The total synthesis of the antiviral marine natural product (-)-hennoxazole A was accomplished by F. Yokokawa and co-workers." The mild reduction of a secondary alkyl azide at C9 was carried out using triphenylphosphine in a THF/water mixture at slightly elevated temperature. The corresponding primary amine was obtained in good yield and was subsequently acylated and converted to one of the oxazole rings of the natural product. 

Staudinger reduction Reduction of azides with triphenylphosphine. 428... 

The 5"-hydroxy group of neomycin B was converted to an amino group by treatment of the 5"-tosylated derivative with sodium azide, followed by reduction of the azide to the amino group by triphenylphosphine in the presence of an aqueous solution of sodium hydroxide. The resulting 5"-amino neomycin B was shown to be a better RNA binder, slowing down the ribozyme cleavage more effectively than the parent compound [73]. 

Aziridino-steroids (e.g. 486) are available by reduction of suitable iodo-azides with lithium aluminium hydride, but fewer side-reactions occur if the iodo-azide (484) is first treated with triphenylphosphine, or with a phosphite ester. Loss of nitrogen leads to the iV-phosphonium aziridine derivative (485), which is smoothly reduced by lithium aluminium hydride to give the aziridine. The exact mechanism of nitrogen loss in the first step is uncertain. 

Hydroxymethyl-1,4-benzodioxin (137) obtained in 80% yield by reduction of ethyl 1,4-benzo-dioxin-2-carboxylate (39) with lithium aluminum hydride in refluxing ether <91TL5525> reacted with zinc azide bis-pyridine complex under Mitsunobu conditions (triphenylphosphine, diisopropyl azodicarboxylate) to yield exclusively compound (138) in 75% yield. Otherwise, (137) was first reacted with zinc iodide under the same conditions until complete transformation of the starting material into the mixture of regioisomers (139) and (140) excess of dry piperidine was then added to the crude reaction medium to yield the alkenic analogue (141) of Piperoxan <89TL1637>. 

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