Disilazanes—

Sodium bis(trimethylsilyl)amide (hexamethyl disilazane sodium salt) [1070-89-9] M 183.4, m 165-167 (sintering at 140 ). It can be sublimed at 170 /2 Torr (bath temp 220-250°) onto a cold finger, and can be recrystd from CgHg (sol lOg in lOOmL at 60°). It is slightly soluble in Et20 and is decomposed by H2O. [Chem Ber 94 1540 1961.]... 

HYPHAT Bis(tetrachlorobenzenediolato)mono(l,2-diarylethanediolato)phosphate(v) LiHMDS Lithium l,l,l,3>3,3-hexamethyl-disilazane... 

The stable P-unsubstituted phosphinous amide H2PN(SiMe3)2 has been shown to suffer the nucleophilic displacement of the disilazane moiety by the action of thiols R-SH giving the phosphinous thioesters R-S-PH2 [13]. For the sake of brevity we shall not comment on other relevant reactions of AT-silyl phosphinous amides, such as the anionic P-silylation [115] and P-alkylation [22], the consecutive dialkylation of PH derivatives [18] and the fluorodesily-lation of P-fluoro-JV-silyl derivatives [140]. 

Analogous reaction of 4-bromobutyric acid 152 with excess N-benzylhexamethyl-disilazane 158 in butyrolactone as polar solvent and added methanol affords, after 1 h at 10 °C, 96% 4-trimethylsilyloxy-N-benzylbutyramide 159, which, on transsilylation with methanol, gives the free crystaUine N-benzyl-4-hydroxybutyramide 160 and methoxytrimethylsilane 13 a [3]. Likewise, reaction of 152 with excess N-2-(tri-methylsilyloxyethyl)hexamethyldisilazane 161 in butyrolactone-methanol affords... 

The cyclic disilazane 2012, which is readily accessible by treatment of 45 with NH3, reacts with the urea-H202 adduct to give, in 68% yield, the liquid cyclic analogue 2013 of BTSP 1249 2013 seems, to be more hindered and thus less reactive than BTSP 1949 [183] (Scheme 12.53). 

Figure 2.6 Reagents used for the deactivation of silanol groups on glass surfaces. A - disilazanes, B > cyclic siloxanes, and C -silicon hydride polysiloxanes in which R is usually methyl, phenyl, 3,3,3-trifluoropropyl, 3-cyanopropyl, or some combination of these groups. The lover portion of the figure provides a view of the surface of fused silica with adsorbed water (D), fused silica surface after deactivation with a trimethylsilylating reagent (E), and fused silica surface after treatment with a silicon hydride polysiloxane (F).

Materials and Purification. Chemicals were purchased from Aldrich chemical company and used as received unless otherwise noted 1,1,1,3,3,3-hexamethyl disilazane, ethylene glycol, triphosgene, poly(ethylene oxide) (MW = 600), poly(tetramethylene oxide) (MW = 1000), poly(caprolactonediol) (MW = 530), toluene diisocyanate (TDI), anhydrous ethanol (Barker Analyzed), L-lysine monohydride (Sigma) and methylene bis-4-phenyl isocyanate (MDI) (Kodak). Ethyl ether (Barker Analyzer), triethylamine and dimethyl acetamide were respectively dried with sodium, calcium hydride and barium oxide overnight, and then distilled. Thionyl chloride and diethylphosphite were distilled before use. 

To explore the feasibility of these polymers as a pendant delivery drug delivery system, 5-fluorouracil activated by 1,1,1,3,3,3-hexamethyl disilazane was coupled to the phosphite via the Todd reaction as shown in Scheme 2. Briefly, the polymer (PPU-7) solution in dimethylacetamide was mixed with a 1 1 v/v solution of carbon tetrachloride and methylene chloride containing 0.5 volume percent of triethylamine (TEA) as catalyst. The activated drug dissolved in methylene chloride was added slowly into the mixture and allowed to react for 48 hours at room temperature. The product was isolated by precipitation into carbon tetrachloride. 

In the past five years, researchers at Dow Corning have made a concentrated effort to explore and develop the use of Si-Cl/Si-N redistribution reactions as a means of preparing tractable, polysila-zane precursors to SijN (3A-A2). Initial work focussed on the reaction of chlorosilanes and chlorodisilanes with hexamethyl-disilazane ... 

With m-phenylenediamine, the unsymmetrical linear disilazane IVb is formed which undergoes recyclization to the unsymmetrical cyclodisilazane mb The following set of equilibria is thus established. 

Similar results were obtained when o-phenylenediamine was reacted with mb. A range of low boiling compounds were separated from the reaction mixture after 10-12 hr heating at 220°C. These have been identified as diazadimethylsilaindane Vb (m.p. 76-78°C lit. (321 m.p. 75-83°C) and bis(phenylamino)dimethylsilane VIb (m.p. 46-48°C lit. (331 m.p, 45 2°C). They are probably formed by thermal decomposition of the intermediate unsymmetrical disilazane IVb". At 190-225°C/0.3 torr, a crystalline fraction with... 

In order to increase the organic solvent solubility of the polymers formed by reaction of 2,4,6-trichloroborazine with a disilazane, Paine et al. proposed the selective use of alkyl- substituted R-chloroborazines as monomers.32 These polymers are intended for materials applications, where the methyl substituent is used to ensure... 

Following these studies, the same authors have reported that the combination of 6-dimethylamino-2,4-dichloroborazine and a disilazane yields two-points polymers (scheme 6).34 Depending on the solvent used and the reaction conditions, the as-prepared polymer is recovered as a gel or as a solid with a low solubility. Subsequently, it is possible to remove the dimethylamino protecting group by the action... 

Andrianov et al. 47) studied the addition of a series of disilazanes, (HSiMe2)2NR (R = H, Et, i-Bu, Ph, PhCH2,p-N02C6H4), to allyldiethyl-amine in anisole at concentrations of silazane, 1 mole/liter amine, 2 moles/liter and H2PtCl -6H20, 1 x 10-4 moles/liter. They measured the rate of disappearance of SiH at 45° and at 57°C. 

With (HMe2Si)2NH and excess allyltrimethylsilane, 20 hours at 80°C brought hydrosilation to completion to make principally HN[Me2Si-(CH2)3SiMe3]2. Under the same conditions the N—Ph disilazane and allylaminotrimethylsilane went 48% to completion. After 20 hours at 160°C, all Si—H had disappeared and PhN[Me2Si(CH2)3SiMe3]2 formed (47). 

The reaction of the bis(trimethylsilyl)methylene-bridged bis(difluoro disilazane) (Me3Si)2C[SiF2(NHSiMe/-Bu2)]2 369 with 2 equiv. of methyllithium has produced the bis(trimethylsilyl)methylene-bridged bis(lithium difluoro... 

Lithium bis(trimethylsilyl)amide (LiHMDS) Disilazane, 1,1,1,3,3,3-hexamethyl-, lithium salt (8) Silanamine, 1,1,1 -trimethyl-N-(trimethylsilyl)-, lithium salt (9) (4039-32-1)... 

A stronger base and notably weaker nucleophile is the anion of hexamethyl-disilazane (Mc3Si)2NH, (34H). The anion, (34) , is electrogenerated ex situ, similarly to (33) , as its magnesium salt in dimethoxyethane with 15% v/v HMPA [75]. The PB (34H) is commercially available, relatively cheap, and in many respects behaves very much Kke lithium diisopropylamide (LDA). Substitution of HMPA with Ai-methyl-2-pyrrolidone was not successful [75]. 

As an experimental proof of the prediction of the calculations, the cyclic disilazane 1,1,3,3-hexamethyl-l, 3-disila-2-aza-cyclopentane was synthesized and its gas phase acidity determined. With the disilazide moiety constrained to a bent geometry within the five-membered ring, the acidity is weakened by 11.5 kcal/mol relative to the acyclic hexamethydisilazane. This places the cyclic disilazane s acidity as essentially within the general trend of gas versus solution phase acidities in Figure 9, and validates the concept that the counterion s locking of the geometry of the anion is the controlling fector in the solution phase acidity of the acyclic form. 

Silicon vinyl derivatives of disiloxanes and disilazanes (173) under conditions of radical polymerization cyclize to form 1,2,5-oxadisila- and -azadisilacyclopentane rings containing polymers <93MM407>. Heating of silene (174) with Ni(PEt3)4 produces among other products 1,2,4-oxadisilacyclopentane (175) <94OMl064>. 

A. Reaction of Disilazanes with Urea-H202 Complex. 814... 

The simple cyclic silyl peroxide, l,l,4,4-teteramethyl-l,4-disila-2,3-dioxane, 75, was prepared by classical synthetic methodology from its corresponding cyclic disilazane 74 and the urea complex of H2O2 (equation 85) . 

Urea-hydrogen peroxide (UHP) crystal structure, 98, 99 disilazane reactions, 814-15 transition metal peroxides, 1083, 1089-90, 1099, 1103, 1113 Uric acid... 

---