Azide From alcohol

Azides from alcohols. On activation with triphenylphosphine and 2,4,4,6-... 

Two new stereospecific syntheses of azides from alcohols, both utilizing phosphorus reagents, have become available (Scheme 23)/ ... 

The sulfonamide betaine 26 has occasionally been employed as a surrogate for TPP/DEAD in Mitsunobu reactions in solution and on solid support. Tamaka et al. have employed 2,4,4,6-tetrabromo-2,5-cyclohexandione (27) as a DEAD equivalent. The couple has been used to convert alcohols and THP ethers into the corresponding bromides. Use of the reagent combination in the presence of zinc(II) azide leads to the efficient formation of azides from alcohols in 70% or higher yields. ... 

Triphenylphosphine/carbon tetrabromide lithium azide Azides from alcohols Preferential replacement... 

There are also useful procedures for preparation of azides directly from alcohols. Reaction of alcohols with 2-fluoro-l-methylpyridinium iodide followed by reaction with lithium azide gives good yields of alkyl azides.75... 

With both building blocks 103 and 109 in hand, the total synthesis of lb was completed as shown in Scheme 17. Coupling of acid 103 and alcohol 109 under Yamaguchi conditions to give ester 110 and subsequent desilylation followed by chemoselective oxidation provided hydroxy acid 111. Lactonization of the 2-thiopyridyl ester derived from 111 in the presence of cupric bromide produced the macrodiolide 112 in 62% yield, which was finally converted to pamamycin-607 (lb) via one-pot azide reduction/double reductive AT-methylation. In summary, 36 steps were necessary to accomplish the synthesis of lb from alcohols 88 and 104, sulfone 91, ketone 93, and iodide rac-97. 

The uniquely distinguished axial alcohol at C5 was activated by triflation and the resultant triflate was displaced by the action of tetra n-butylammonium azide in benzene at room temperature. Compound 25 was thus available in 86% yield from alcohol 24. Hydrogenolysis ((H24 d(OH)2C) followed by acetylation afforded compound 26 in 96% yield. TTie richly detailed NMR spectrum (490 MHz) of 26 was identical in every respect with that of the L-antipode derived from reaction of NeuSAc, first with acidic methanol and then with benzoyl chloride under the influence of DMAP. The infrared and mass spectra, as well as the chromatographic characteristics of the two materials, were identical. 

Support-bound isocyanates can be conveniently prepared from carboxylic acids by Curtius degradation. Because the reaction of the intermediate acyl azides with alcohols to yield esters is slow, Curtius degradation can be conducted in the presence of alcohols to yield carbamates directly (Entries 4 and 5, Table 14.8). 

Direct displacements of the hydroxyl group by azide are uncommon, but carbonium ions derived from alcohols are attacked by the azide ion to give organic azides (43) (Reaction XXVIII). 

The reaction of an alcohol and a carboxylate anion with diethyl azodicarbox-ylate EtOOCN=NCOOEt and PhsP is called the Mitsunobu esterification reac-tion. This reaction can also be considered as an 8 2. Other Mitsunobu catalysts are available, " and a polymer-bound phosphine has been used. A renewable phosphine ligand has been developed. Note that other functional groups, including azides and thiocyanates can be generated from alcohols using Mitsunobu conditions. 

Pt(III) intermediates. The pressure dependence of the quantum yield for the reductive elimination of azide from [frans-Pt(CN) (N,)2] to give [Pt(CN) ] has been exeunined auid the results interpreted in terms of formation of a caged radical species via simultaneous scission of both Pt-N, bonds in the charge-treuisfer excited state. - Alcohols have been oxidised in a two electron process at room temperature by O2 in the presence of a H PtCl /CuCl catalyst. A cyclic process incorporating a Pt(III) species % ich undergoes a redox reaction with Cu(II) to regenerate the Pt(IV) catalyst appears to be involved. 14. Copper... 

Dry, unconfined lead azide was initiated by impact from lower heights than the confined material. Unconfined mixtures of lead azide and water, lead azide and alcohol, and lead azide and Freon TF were less sensitive than dry, unconfined lead azide. 

Sulfonates. The sulfonates derived from alcohols and the title reagent are good electrophiles toward azide and cyanide ions. 

Alternatively, Schultz and coworkers [59] have proposed an approach related to that of Burgess which utilizes azido 4-nitrophenyl carbamates 98 as activated monomers. Carbamates 98 were prepared in four steps from alcohol 95. Mesylation of 95 followed by azide displacement afforded the A-Boc-protected azide in high yield (80-90%). Boc deprotection and treatment of the resulting free amine with / -nitrophenyl chloroformate in the presence of pyridine in THF provided 98 (50-90% for the two steps). Solid-phase urea bond formation was performed on a Rink amide resin by coupling 98 (5 equiv.) in CH2CI2 in the presence of DIEA (7 equiv.) for 4 h at room temperature. Support-bound azide 99 was reduced in less than 2 h using... 

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