Sodium bistrimethylsilylamide

Methylation at the 9a-position of the A3,11-diketone (23) to yield (24) has been achieved by reaction of (23) with sodium bistrimethylsilylamide and methyl iodide. The base is soluble in most organic solvents and this facilitates rapid and almost quantitative conversion of a ketone into its enolate. 

Serini reaction, 167 Simmons-Smith reaction, 107 Sodium acetylide, 138 Sodium bismuthate, 147, 149 Sodium bistrimethylsilylamide, 90 Sodium chloroacetylide, 68 Solvolytic cleavage of cyclic ethers, 267 3- (5 -Spiro-2, 2 -dimethyloxazolidi nyl) -cholestane, 360... 

Based on the early racemic synthesis of 4 (cis series), it had already been demonstrated that 2-azetidinone ring closure could be achieved via nucleophilic attack of a lithium amine anion on a (3-ester. Cyclization could be accomplished with other strong bases, but sodium bistrimethylsilylamide was found to effect efficient cyclization without significant racemization at C3. During the search for experimentally convenient bases, it was noted that Noyori (Nakamura et al., 1983) reported that tetrabutylammonium fluoride (TBAF) as well as LiF, KF, and CsF could serve as the base in Aldol reactions. Treatment of 17a or 17b with TBAF trihydrate in THF did not affect cyclization. After much experimentation it was found that addition of A,0-bistrimethylacetamide (BSA) to 19 followed by TBAF addition, effected 2-azetidinone ring closure. Further optimization found that use of catalytic TBAF (< 1%) in methylene chloride afforded near quantitative cyclization. 

Silver trifluoroacetate, 327, 328 Silyl ethers, 477-478 Simmons-Smith reagent, 436-437 (3-Sinensal, 283 Sirenin, 424 Sodium, 246, 268, 437 Sodium acetate, 578 Sodium aluminum chloride, 438 Sodium aluminum diethyl dihydride, 438 Sodium aluminum hydride, 316 Sodium amalgam, 41,438-439 Sodium amide, 231, 305,403,439 Sodium amide-Sodium f-butoxide, 439-440 Sodium-Ammonia, 26, 32,134, 260,438 Sodium azide, 9, 77, 210, 323, 440-441 Sodium benzoxide, 111 Sodium bis-(2-methoxyethoxy)aluminum hydride, 164, 293, 360,441-442 Sodium bistrimethylsilylamide, 442-443,... 

METHYLTHIOMETHYL ESTERS Chlo-romethyl methyl sulfide. MONOBROMOCYCLOPROPANES Sodium bistrimethylsilylamide. NAPHTHALENE 1,2-oxide ... 

Sodium bistrimethylsilylamide (2). Mol. wt. 183.39, m.p. 165-167°. Preparation from hexamethyidisilazane and a suspension of sodium amide in benzene "... 

Cyclization Aluminum chloride. Phosphoric-Formic acid. Polyphosphoric acid. Sodium aluminum chloride. Sodium bistrimethylsilylamide. Stannic chloride. 

Wrrno reaction, bases n-Butyllithium (see Potassium t-butoxide). Lithium ethoxide. Potassium t-butoxide. Sodium bistrimethylsilylamide. Sodium ethoxide (see Potassium t-butoxide). Sodium bydride-Dimethyl sulfoxide [see DMSO-derived reagent (a)]. Sodium methoxide. 

Formation of the ylid requires a suitable base and whilst several have been used (see examples which follow), particularly good results are claimed for sodium bistrimethylsilylamide at —78 °C. 

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