Trimethylsilyl azide-lead

There are also a series of papers on the formation of rings containing two or three nitrogen atoms. For example, the action of heat on cz s -tetrahydroisatoic anhydride (7) with trimethylsilyl azide leads to compounds 8 (yield 37%) and 9 (yield 34%), also having the cis configuration [6],... 

The analogous chromium complex was used in the asymmetric ring opening of meso epoxides with trimethylsilyl azide [15] (Scheme 4). In this case a strong dependence on the anion of the ionic hquid was observed. Anions leading to hydrophobic ionic hquids, such as PFe" and SbFe", led to high... 

Deprotection of N-2 by ozonolysis furnishes triazoles 1225 (Scheme 202) <2003JA7786>. Finding that 1,3-dipolar cycloaddition of alkynes 1222 to trimethylsilyl azide, carried out in DMF/MeOH in the presence of Cul as a catalyst, leads directly to products 1225 with much higher yields provides a significant progress to the synthesis of N-unsubstituted 1,2,3-triazoles <2004EJO3789>. 

Gilardi and co-workers reported a synthesis of 4-(trimethylsilyl)-5-nitro-1,2,3-triazole (136) via a cycloaddition between l-nitro-2-(trimethylsilyl)acetylene (134) and trimethylsilyl azide (135). This may provide a route to 4,5-dinitro-l,2,3-triazole via nitrodesilylation or lead to the synthesis of 4-amino-5-nitro-l,2,3-triazole, an isomer of ANTA. 

The addition of aryl azides to cyclic dienes in which both double bonds are strained, leads to the formation of mono- or bistriazoline adducts.25,97,98,104,115,146-148 A monoadduct is not obtained from the reaction of trimethylsilyl azide and norbornadiene, inasmuch as it is less stable than the bisadduct and undergoes a retro Diels-Alder reaction (Section IV,A,5).104 The formation of two exo isomers of the bisadduct, with the trimethylsilyl groups in the syn and anti positions, is indicated by the NMR spectrum,104 although the isolated product is the anti isomer. 

The generation of intermediate azidothiocarbonyl compounds 10 followed by 1,5-electrocyclic reaction leads to 5-substituted 1,2,3,4-thiatriazoles 9. This mechanism has been proposed in reactions of various derivatives of thiohy-drazides 136 with either nitrous acid or arenediazonium salts, and in reactions of thiophosgene (or dithiocarboxylates) 135 (X = C1, SR) with either sodium or trimethylsilyl azide (Scheme 32) <1984CHEC(6)579, 1996CHEC-II(4)691,... 

Hydrazoic acid, HN3 can be generated either from sodium azide and an aqueous acid [14] or from trimethylsilyl azide and MeOH [31], and its application leads to the formation of primary amines in good to excellent yields [32] (Scheme 12). 

The exposure of aromatic ethers to BTIB in (CF3)2CHOH or CF3CH2OH (TFE) leads to arene cation-radical intermediates and permits the introduction of nucleophiles (N, AcO-, NCS-, ArS-) into the alkoxyarene nucleus (94JA3684, 95JOC7144). For example, the treatment of / -substituted anisoles with BTIB in the presence of trimethylsilyl azide or -isothiocyanate affords the 2-anisyl azides 98 or 2-anisyl thiocyanates 99, respectively (Scheme 30). 

Trimethylsilyl azide, (TMSN3) reacts with carbon-carbon double bonds to form a compound which can be cleaved by lead tetraacetate (or phenyliododiacetate) to yield a carbonyl and a nitrile, as in equation (37).The reagent has been tqrplied extensively to the cleavage of unsaturated steroids, as illustrated in equation (38). 

Furthermore, cycloaddition reactions have been carried out between metal acetylides and azides leading firstly to triazole triazene salts (241). On hydrolysis the corresponding triazole azide (242) is obtained (ssjociosi). The addition of trimethylsilyl azide to alk5oies occurs at higher temperatures, but due to the considerable thermal stability of the azide, good yields of triazoles (243) can be achieved (sommiioi). 

Review. The reagent is prepared by mixing lead tetraacetate and trimethylsilyl azide (1, 1236 3, 316) inaprotic solvents at —40to -20°. 

Trimethylsilyl azide (TMS-A) in the presence of catalytic amounts of pyridine turned out to be very useful in the preparation of acyl azides, as this reagent will not only transform acyl chlorides and mixed anhydrides into azides, but also works with reactive esters and lactones (Scheme 40). 2 - 4S Many of these reactions have, however, been run under conditions which will lead to the Curtius rearrangement of the azide intermediates. Pyridine as a catalyst can be replaced by the combination KNa/18-crown-6. Diazidodiphenylsilane, which was investigated as well, will probably not become a standard reagent. 

A convenient synthesis, which leads toA-hydrogen-l,2,3-triazoles, utilises the stable (and relatively safe) trimethylsilyl azide. Alternatively, by conducting a cycloaddition in the presence of formaldehyde, A-hydroxymethyl-triazoles are formed (mainly the 2-isomer from isomerisation of initially formed 1-hydroxymethyl-triazole) from which AT-unsubstituted heterocycles can be easily obtained using base azidomethanol is formed in situ and is the entity that adds to the alkyne. ... 

A mixture of either lead tetra-acetate or phenyliodosoacetate with trimethylsilyl azide apparently acts as a source of electrophilic azide at —15 °C, although free-radical reactions predominate when lead tetra-acetate is used at higher temperatures (see p. 314). The ionic reaction seems best represented as in Scheme 9, probably giving the unstable IV-diazonium-aziridines (171) and (172). The isolated products from trisubstituted olefins (e.g. cholesteryl acetate) are... 

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