Nitrodesilylation

No kinetic studies, which have yielded rate coefficients of nitrodesilylation 

The mechanism of the reaction has been interpreted in terms of a 4- or 6-centre transition state (LV) or (LVI) in which nucleophilic assistance of C-Si bond cleavage occurs this would not be possible for nitration by nitronium tetrafluoroborate. 

The use of oxetanes for the synthesis of polynitrate esters is generally of less value than the use of epoxides, which are readily available from the epoxidation of alkenes. The analogous reaction of azetidines with dinitrogen pentoxide is a route to 1,3-nitramine-nitrates and these reactions are discussed in Section 5.8.2.  

Cyclic formals react with dinitrogen pentoxide in chlorinated solvent to yield unstable but interesting ring-opened products, including hemiformal nitrates 1,3-dioxolane (44) reacts to yield a mixture of hemiformal nitrate (45) and formal ether (46) products. Similar products are formed from acyclic formals and dinitrogen pentoxide.  

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A decrease in the nitric acid concentration caused R to decrease as it did during a particular run (in which the acid concentration would decrease with time). Thus nitrodesilylation would seem to be of higher order than nitrodeprotonation. 

Nitrodesilylation (Eq. 2.17)36 and nitrodestanylation (Eq. 2.18)37 are efficient methods for the preparation of some kinds of nitroalkanes from readily available alkylsilanes or allylstan-nanes. Similar nitration also takes place at the vinylic positions (see Eq. 2.36 in Section 2.1.4). 

Olah and co-workers reported the synthesis of nitroalkanes and nitroalkenes from the nitrodesilylation of alkylsilanes and allylsilanes, respectively, with nitronium salts. 

Nitroacetylenes are generally unstable and very explosive and so they have been little studied. Schmitt and co-workers used the nitrodesilylation of trialkylsilylacetylenes with both nitronium salts and nitryl fluoride to obtain nitroacetylenes. Dinitrogen pentoxide has also been used for the nitrodesilylation of trialkylsilylacetylenes. Nitrodestannylation of allylsilanes has also been reported. " ... 

Millar and Philbin have explored the nitrodesilylation of silylamines with dinitrogen pen-toxide for the synthesis of nitramines and their derivatives. These reactions, which involve nitra-tive Si-N heteroatom cleavage, are conducted in methylene chloride at subambient temperature. Trimethylsilylamines give high yields of nitramine product and reactions are clean (Table 5.8). 

Synthesis of nitramines, nitramides and nitroureas via the nitrodesilylation of A/-trimethyisilyl compounds with dinitrogen pentoxide (ref. 122)... 

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. 

Nitrodesilylation. Silyl ethers and silylamines are converted to nitrate esters and nitramines, respectively, at about 0°. 

Schmitt et al. [97,98] obtained in high yield nitroacetyJenes by the nitrodesilylation of trimethylsilylacctylenes. 

Olah and Narang [148] found that reaction of nitronium tetrafluorobo-rate with phenyltrimethylsilane gives only limited (10%) nitrodesilylation besides intact (predominantly para) ring nitration. 

Nitrodesilylation with nitronium tetrahuoroborate is also a mild and efficient way to prepare aiiphatic nitrocompounds from readily available alkylsilanes. Olah and Rochin have studied [151] the scope of the reaction, Tetramethylsilane reacts readily with NOJBFJ in sulfolane solution to give nitromethane in 80% yield. 

Nitrodesilylation probably proceeds via the pentacoordinafc two electron three-center bonded siliconium ion. 

On the other hand, benzylsilanes do not undergo nitrodesilylation. but instead ring nitration takes place. 

Although alkylsilanes, as discussed, undergo nitrodesilylation with NO2 BF4, organostannanes in preference undergo one-electron oxidation with nitronium salts. 

Nitramines can be obtained by nitrodesilylation of silylamines which can provide a route for the synthesis of certain nitramines heretofore unobtainable by conventional nitration methods. 2-Isopropyl-l,4-dinitioi dazole was synthesized by nitration of the corresponding silylated derivative [154]. 

Millar RW, Phibin SP (1997) Clean nitration novel syntheses of nitramines and nitrate esters by nitrodesilylation reactions using dinitrogen pentoxide (N2O5). Tetrahedron 53(12) 4371-4386... 

Nitro compounds from silanes and germanes Partial nitrodesilylation s. 16, 515... 

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