Azides reductive cleavage

The alcohol 177 was converted to starting substrates oxazolidinone 178 by acylation followed by reduction of the azide function along with cyclization. Oxazolidinone 178 was protected with f-butylpyrocarbonate-4-(dimethylamino) pyridine (DMAP) and triethylamine, which was further subjected to reductive cleavage of the benzyl ester unit to afford carboxylic acid 179. The treatment of 179 with solution of l-chloro-/V./V,2-trimethyl-1-propenv I airline resulted in the easy formation of the corresponding acid chloride which on reaction with imine in the presence of triethylamine provided the stereoselective formation of spiro-p-lactam 180. 

Fig. 4. Reductive cleavage of a /i-oxobisiron(III) complex with subsequent binding of azide to the unreduced iron atom.

Reaction of aryl azides with hydrazine hydrate can result in reductive cleavage of the azido group. Azidobenzene gives a mixture of benzene and aniline when heated with an excess of hydrazine hydrate in ethanol. If there is an acyl or an alkoxycarbonyl group at the ortho position, cyclization products are formed instead for example, methyl 2-azidobenzoate gave indazolinone (13 90%). 

The reductive cleavage of benzoyl azide rans at low temperature with tetracarbonylhydridofeirate, [HFe(CO)4] and with diphosphorus tetraiodide in benzene under reflux. Curtius rearrangement side products are not observed. 

Organometallic complexes of uranium(vi) with organoimido and oxo functional groups Cp 2U(=NR)(=E) (E = NR or O) have also been prepared by two-electron oxidative atom transfer using organic azides, amine A-oxides or nitrous oxide. Another way of generating the compounds is reductive cleavage of 1,2-disubstituted hydrazines (Scheme 54).119-121... 

Chiral 1,2,3,4-tetrahydroisoquinolines are accessible from 0-carbamyl lactates via N-oxaacyliminium cyclization (Scheme 31). The precursor for the generation of the chiral N-oxaacyliminium ion 220 is prepared by reaction of (5)-methyl lactate (97) with azide 217 followed by partial reduction of 218 with diisobutylaluminum hydride. Cyclization of 219 with formic acid at room temperature for 14 h gives the oxazolo[4,3- 2]isoquinoline (221) without racemization [78]. Reductive cleavage of the oxazoline ring with lithium aluminum hydride furnishes the corresponding l-hydroxyalkyl-l,2,3,4-tetrahydroisoquinoline in 98% yield. 

As reported in 1902, the substrate scope of the Dimroth triazole synthesis was limited to aromatic azides. An early extension of this methodology was reported in 1956 by Hoover and Day at the University of Pennsylvania. IH-1,2,3-Triazoles were of particular interest at the time as potential modifiers of nucleic acid metabolism. As part of a program directed at cancer chemotherapies, they replaced the azide aromatic moiety with a benzyl substituent. Sodium ethoxide-promoted reaction of benzyl azide (19) with active methylene compounds 25 provided 1-benzyl-1,2,3-triazoles 26 that could undergo reductive cleavage with sodium in liquid ammonia to afford the desired 4,5-disubstituted species. While various active methylene compounds were successfully used (ethyl cyanoacetate, cyanoacetamide, cyanoacetic acid, and malononitrile), the yields were low to modest when compared with aromatic substrates. ... 

Gayen, K. S., Sengupta, T., Saima, Y., Das, A., Maiti, D. K., and Mitra, A. 2012. Cu(0) nanoparticle catalyzed efficient reductive cleavage of isoxazohne, carbonyl azide and domino cycUzation in water medium. Green Chem. 14(6) 1589-1592. 

Reductive cleavage (triethylsilane-trimethylsilyl triilate) of the isopropylidene derivatives 17 gives anhydro-sugars 18. The OH-2 groups in 18 have been further converted to mediates and displaced with purine bases or azide (further converted into a pyrimidine ring) to lead to nucleoside analogues. ... 

Triazoles are obtained via 1,3-dipolar cycloadditions between azides and al-kynes, and they are probably the most common nitrogen heterocycles prepared on solid supports via 1,3-dipolar cycloaddition. A wide variety of 1,2,3-triazoles have been prepared on solid supports, with an alkyne or azide attached to the resin. In addition, various linkers have been studied. Alkyne-functionalized alcohol was attached to the MeOPEG resin with an oxalyl chloride linkage (Scheme 11.23). Cycloaddition of alkynes with carbohydrate-derived azides gave resin-bound 1,2,3-triazoles, and reductive cleavage with sodium borohydride released the products as primary alcohols. 

They served for the preparation of halohydrins (after reductive cleavage from the auxiliary) and epoxides but were also used as intermediates en route to a-amino acids via azide substitution of the halide, saponification, and hydrogenolysis of the azide. 

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