Azides phosphoramidates

Several approaches to the 1,2,3-triazole core have been published in 2000. Iodobenzene diacetate-mediated oxidation of hydrazones 152 led to fused 1,2,3-triazoloheterocycles 153 <00SC417>. Treatment of oxazolone 154 with iso-pentyl nitrite in the presence of acetic acid gave 1,2,3-triazole 155, a precursor to 3-(W-l,2,3-triazolyl)-substituted a,P-unsaturated a amino acid derivatives <00SC2863>. Aroyl-substituted ketene aminals 156 reacted with aryl azides to provide polysubstituted 1,23-triazoles 157 <00HC387>. 2-Aryl-2T/,4/f-imidazo[43-d][l,2,3]triazoles 159 were prepared from the reaction of triethyl AM-ethyl-2-methyl-4-nitro-l//-imidazol-5-yl phosphoramidate (158) with aryl isocyanates <00TL9889>. 

The thermolytic behavior of triazolines formed by the addition of phosphoryl azides to norbornenes differs from related compounds imines (phosphoramidates) are the sole decomposition products.105,466,477,478 The rate of decomposition is described by two consecutive first-order reactions, formation of the betaine in the first step and nitrogen expulsion in the... 

In the palladium-catalyzed allylic amination reaction, primary and secondary amines can be used as nucleophiles, whereas ammonia does not react. Therefore, many ammonia synthons have been developed, and a variety of protected primary allyl amines can now be prepared using azide, sulphonamide, phthalimide, di-f-butyl iminocarbonate ((Boc)2NLi), and dialkyl A-(rerr-butoxycarbonyl)phosphoramide anions as the nucleophile [20], An example of the use of ((Boc)2NLi) 30 as the amine nucleophile in the palladium-catalyzed allylic amination reaction is shown in Eq. (9). This reaction also illustrates the problem with the regioselectivity in the reaction as a mixture of the products 31-33 are obtained [21]. 

Attack on Nitrogen. A new route to phosphoramidates, involving the reaction of silyl phosphites with the appropriate azide, followed by hydrolysis, has been developed. The mechanism (see Scheme 6) probably involves initial formation of the phosphite imine (36) followed by migration of a sUyl group from oxygen to nitrogen, and it is exemplified by the synthesis of the oligoazanucleotide (37). 

A new method for the preparation of 5 -amino-5 -deox)mucleotides has been described, based on the reaction between phosphorus triesters and phenyl azide. Treatment of protected 5 -azido-5 -deoxynucleosides with trimethyl or triphenyl phosphite leads, after removal of the nucleoside protecting groups and one of the esterifying groups from the phosphoryl residue, to the phosphoramidates (9). Snake venom phosphodiesterase hydrolyses (9) to 5 -aminonucleosides. 

The highly reactive nitrenes derived from phosphoryl azides do not readily undergo rearrangement. They also appear to have a low selectivity with respect to —H insertion reactions. Thus, irradiation of diethylphosphoryl azide (143 R = Et) in cyclohexane, for example, led to formation of diethyl cyclohexyl-phosphoramidate (144 R = Et) in 88% yield.83 A lower yield (67%) of insertion product, diphenyl cyclophosphoramidate (144 R = Ph), was obtained on... 

The reaction of glycosyl azides with phosphates has proved less popular, but it was first studied with acetylated pentopyranosyl azides and the products are glycosyl phosphoramidates (glycosyl amidophosphates). Paulsen et demonstrated this transformation with o-manno-heptose derivatives. The oc-azide... 

Ashfeld and coworkers proposed that the initial phosphinylation of oxime 2 and subsequent Staudinger-like reduction of the tosyl azide forms iminophosphorane 171 (Scheme 5.42k The formation of the phosphoryl bond upon rearrangement is a likely driving force behind the regioselective migration of the trans-oxime substituent (R in 171) to afford the nitriliumion 5. The corresponding anionic phosphoramide is released and then adds to the nitrilium ion amidine 17. A subsequent 1,3-phosphoryl shift leads to the final amidine product 173. 

Basic hydrolysis of the products from the reaction of 3-P-D-ribofuranosyl-adenine with phosphorus oxychloride in trimethyl phosphite gave the cyclic phosphoramidate (620) as well as the expected 5 -phosphate. Phosphoramid-ates e.g. (621)] have been obtained from the reaction between nucleoside 5 -azides and 3 -silylphosphites the silylation reaction and azide condensation were conducted simultaneously (Scheme 95). ... 

Finally, another important class of Si-N linkages consists in the azide modified Si surface (Si-N ), which can again be prepared from either Si-Cl or Si-H surfaces. Direct grafting of azide functional groups on monochloride-covered (111) Si surfaces can be obtained by a room temperature treatment with NaN in either hexamethyl-phosphoramide (HMPA) or methanol for 5 min and 3 h, respectively [217]. 

Phosphoramidation of the arene (5) C-H bonds with phosphotyl azides (6) has been realised in the presence of an iridium catalyst. This reaction was compatible with several directing groups such as pyridinyl, pyrazoyl, and quinolinyl, and provided AT-atyl phosphoramidates (7) in moderate to good yields (Scheme 3). ... 

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