Tert-butyldiphenylsilyl chloride, reaction

Tin-based reagents are not always snitable owing to the toxicity of organotin derivatives and the difficulties often encountered in removing tin residues from the final product. Therefore, the same authors have carried out additional experiments with 17d and several different alkyl halides under tin-free conditions. The treatment of 16d with tert-butyldiphenylsilyl chloride (TBDPSCl) and triethylamine in the presence of silver triflate in CH2CI2 affords the bis(silyloxy)enamine 17d in 92% yield (Scheme 17). When the radical reaction was carried out with ethyl iodoacetate in the presence of 2,2 -azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70) as the initiator in CH2CI2, the oxime ether 19 was obtained in 83% yield (Scheme 17). 

The procedure outlined above describes the selective, retentive, p-coupling of (Z)-2,3-dibromopropenoic acid ethyl ester with (trimethylsilyl)acetylene employing the palladium-modified version of the Castro-Stephens reaction.4 5 The dibromide starting material is readily available by bromination of ethyl propiolate (Procedure A), as described by Trippett and Hall.2 The coupling product has been shown to be a versatile precursor for the synthesis of variously substituted enynes and enediynes. For example, a second acetylene may be introduced into the a-position under modified coupling conditions. Alternatively, reduction of the ester with diisobutylaluminum hydride and protection of the resultant alcohol with tert-butyldiphenylsilyl chloride affords a vinyl bromide that can be metalated and trapped with various electrophiles. These procedures have been used on the gram and multigram scale.5... 

To a solution of sucrose (1.000 g, 2.92 mmol) in dry pyridine (15 mL) was added 4-dimethylaminopyridine (0.05 g) and 1.1 mol equiv. tert-butyldiphenylsilyl chloride (0.884 g, 3.21 mmol). The reaction mixture was placed in the microwave oven and irradiated at 90°C and power of 300 W for 5 min. The reaction mixture was concentrated and chromatographed (ethyl acetate l00 100 l ethyl acetate-acetone-water- 10 10 l ethyl acetate-acetone-water), to yield first 6,6 -di-0-tert-butyldiphenylsilyl-sucrose (0.238 g, 10%), which was identical in all respects to substance 5 described below. 

Highly enantiosele ctive annulation reactions of (tert-butyldiphenylsilyl)allenes with ethyl glyoxylate using bis(oxazolinyl)pyridine-scandium triflate complex was described [120]. This [3 + 2] cycloaddition gave the corresponding dihydrofurans in moderate to high yields with high enantioselectivities (Scheme 12.54). The vinyl-silane functionality was acylated in Friedel-Crafts reaction with acetyl chloride to produce a-alkoxyenone. 

Retention of configuration. A soln. of BBr3 in methylene chloride added to a soln. of (R)-(-)-2-octyl rr-butyldimethylsilyl ether in the same solvent at 0°, stirred at room temp, for 10 min, and treated with satd. NaHC03 - (-)-2-bromooctane. Y 90% (71% retention of configuration). With Ph3PBr2 (Synth. Meth. 42, 480) reaction proceeds with inversion of configuration. Tert., sec., benzylic and allylic silyl ethers were cleaved more rapidly than prim, silyl ethers. With allylic ethers, double bond shift takes place. F.e. inch cleavage of rr-butyldiphenylsilyl ethers s. S. Kim, J.H. Park, J. Org. Chem. 53, 3111-3 (1988). 

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