Azide addition reactions

Interestingly, when MEM azide addition reactions are carried out at temperatures ranging from 60- 140°C, in addition to the formation of the azafulleroid and azirenofullerene, a bisazafulleroid (diazabishomofullerene) 8 is formed and is the major product [37]. For reasons which are not well understood, the double bonds adjacent to the nitrogen bridge are more reactive towards further cyclo-... 

The reactions of amides fall into hydrolysis, dehydration and degradation (to amines) acid hydrazides and acid azides undergo additional reactions. 

The reactions of enamines as 1,3-dipolarophiles provide the most extensive examples of applications to heterocyclic syntheses. Thus the addition of aryl azides to a large number of cyclic (596-598) and acyclic (599-602) enamines has led to aminotriazolines which could be converted to triazoles with acid. Particular attention has been given to the direction of azide addition (601,603). While the observed products suggest a transition state in which the development of charges gives greater directional control than steric factors, kinetic data and solvent effects (604-606) speak against zwitterionic intermediates and support the usual 1,3-dipolar addition mechanism. 

Aziridines can be prepared directly from double-bond compounds by photolysis or thermolysis of a mixture of the substrate and an azide. The reaction has been carried out with R = aryl, cyano, EtOOC, and RSO2, as well as other groups. The reaction can take place by at least two pathways. In one, the azide is converted to a nitrene, which adds to the double bond in a manner analogous to that of carbene addition (15-62). Reaction of NsONHC02Et/ CuO [Ns = A(/7-toluenesulfonyl-inimo)] and a conjugated ketone, for example, leads to the A-carboethoxy aziridine derivative.Calcium oxide has also been used to generate the nitrene.Other specialized reagents have also been used." ... 

Sulfonylnitrenes are formed by thermal decomposition of sulfonyl azides. Insertion reactions occur with saturated hydrocarbons.255 With aromatic compounds the main products are formally insertion products, but they are believed to be formed through addition intermediates. 

Nitrilium salts, e.g., 66, prepared from the alkylation of nitriles, react with sodium azide to yield 1,5-disubstituted tetrazoles, e.g., 67 (Scheme 7).121 The Schmidt reaction,122 a versatile method for the preparation of 1,5-disubstituted tetrazoles from ketones and hydrazoic acid, can now be regarded as a special case of azide addition to nitrilium salts.123... 

Besides addition reactions, azides or hydrazoic acid can also yield tetrazoles through displacement reactions. Thus, halide displacement in imide chloride (78) yields 1,5-disubstituted tetrazoles (79), and in 2-chloro-pyridine (80), yields tetrazolopyridine (81) (Eq. 16a,b).141 143 Vinylogous... 

Complex 165 reacts with CO at room temperature to give />-tolyl isocyanate and the golden dicarbonyl compound 166. The latter can also be generated by reaction of 164 with excess of CO and converted back to imide 165 by the addition of 2 equiv of /> toly 1 azide (2003JA322). Reaction of cobalt(m) imide 167 analogous to 165, available from [PhB(CH2PPh2)3]CoI 156 by the same procedure as for 165, with CO proceeds similarly <2002JA11238>. 

Buchanan and coworkers71 prepared the /3-D-ribofuranosyltriazole 287 by dipolar addition of benzyl azide to the /3-d-ribofuranosylethyne 70. Related analogs have been reported by others.113a,205a,205b The anomeric 3-phenyl-4-D-ribofuranosylpyrazoles have been prepared by a dipolar, addition reaction.2050... 

A reaction known as diazo group transfer produces diazo barbituric acid from barbituric acid and p-toluene sulfonyl azide. Additional barbituric acid affords azo barbituric acid [7]. Subsequent complexation with a nickel (II) salt yields a greenish yellow pigment. 

A number of addition reactions to the salt (150) have been reported.140 With azide ion, the ylide (151) is formed. Diels-Alder addition of cyclopentadiene occurs to form isomeric adducts (152). With thioamides, a mixture of the salts (153) and (154) results, and with, e.g., 2-aminopyridine, the salt (155) is formed. 

Addition reactions of silylphosphines to imines have been reported, 4 as illustrated for diethyl(trimethylsilyl)phosphine (70). Organic azides react with germylphosphines by an insertion pathway,65 as shown for various phenyl(trimethylgermyl)phosphines (71). The initial products (72) isomerize to phosphine imines on heating.66... 

Workentin et al. (1994) described another interesting solvent effect on the competition between electron transfer and the addition reaction between organic cation-radicals and azides. TEE and AN were compared as solvents. In TEE, the cation-radicals of 4-methoxystyrene (R =R =H), P-methyl-4-methoxystyrene (R =Me, R =H), or p,p-dimethyl-4-methoxystyrene (R =R =Me) react with the azide ion according to the following equation ... 

Group-transfer polymerizations make use of a silicon-mediated Michael addition reaction. They allow the synthesis of isolatable, well-characterized living polymers whose reactive end groups can be converted into other functional groups. It allows the polymerization of alpha, beta-unsaturated esters, ketones, amides, or nitriles through the use of silyl ketenes in the presence of suitable nucleophilic catalysts such as soluble Lewis acids, fluorides, cyanides, azides, and bifluorides, HF. ... 

The utilization of a-amino acids and their derived 6-araino alcohols in asymmetric synthesis has been extensive. A number of procedures have been reported for the reduction of a variety of amino acid derivatives however, the direct reduction of a-am1no acids with borane has proven to be exceptionally convenient for laboratory-scale reactions. These reductions characteristically proceed in high yield with no perceptible racemization. The resulting p-amino alcohols can, in turn, be transformed into oxazolidinones, which have proven to be versatile chiral auxiliaries. Besides the highly diastereoselective aldol addition reactions, enolates of N-acyl oxazolidinones have been used in conjunction with asymmetric alkylations, halogenations, hydroxylations, acylations, and azide transfer processes, all of which proceed with excellent levels of stereoselectivity. 

Systematic investigations of twofold additions of malonates to C70 revealed that the second addition takes place at one of the five a-bonds of the unfunctionalized pole [17, 26], With achiral, C2v-symmerical malonate addends, three constitutionally isomeric bisadducts are formed An achiral one (C2v-symmetrical 1), and two chiral ones (C2-symmetrical 2 and 3), which are obtained as pairs of enantiomers with an inherently chiral addition pattern (Figure 13.5). Twofold addition of chiral malonates leads to the formation of five optically active isomers, two constitutionally isomeric pairs of C2-symmetrical diastereomers and a third constitutional C2-symmetrical isomer (Figure 13.5). Twofold additions of azides to C70 lead to diazabis[70]homo-fullerenes, which served as starting material for the synthesis of bis-(aza[70]-fullerenyl) (Cg9N)2 (Chapter 12) [27]. As further bisadditions, addition reaction to C70 [2+2]cycloaddition of electron-rich bis(diethylamino)ethyne and 1-alkylthio-2-(diethylamino)ethynes [28] and the addition of transition metal fragments have been reported [29-32],... 

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