Rearrangements hexamethyldisilazide

Spirocyclic oxindole 60 was synthesized by [3,3]-sigmatropic rearrangement of the Af-phenyl-O-acylhydroxamic acid 58 (equation 19). The potassium enolate formed by treatment of 58 with potassium hexamethyldisilazide at low temperature rearranged to 59, which easily cyclized to the spirocyclic oxindole 60. Spirooxindoles were previously synthesized by Wolff and Taddei. The spirooxindole 60 was formed in 51% yield from cyclohexanecarboxylic acid after heating the preformed lithium salts of phenyl hydrazide 61 to 205-210 °C. [Pg.357]

Silyl enolates generated from a-allyloxy ketones undergo the [2,3]-Wittig rearrangement in the presence of a catalytic Lewis base such as lithium 2-pyrrolidone, lithium acetamide, or lithium hexamethyldisilazide (Scheme ll).15... [Pg.435]

Ester enolate Claisen rearrangement (4, 307- K)8 6, 276-277 7, 209-210). Lithium hexamethyldisilazide is comparable to LDA in combination with HMPT for stereoselective Claisen rearrangement of ester cnolates. ... [Pg.280]

Potassium hydride and potassium hexamethyldisilazide are the most commonly used metal sources to generate the alkoxide . But recently, the indium(I)-mediated tandem carbonyl addition-oxy-Cope rearrangement of y-pentadienyl anions to cyclohexenones and conjugated aromatic ketones has been reported. For example, indium alkoxide 8.32, obtained after the addition of 5-bromopenta-1,3-diene (8.31) to the aromatic conjugated ketones 8.30, undergoes a spontaneous oxy-Cope rearrangement to give 8.33 in 55% yield (Scheme 8.9). [Pg.353]

Simmons-Smith cyclopropanation, 456 Simmons-Smith reaction, 455 six-centered transition state, 264 Smiles-type rearrangement, 7 SOCI2, 19, 159 sodium azide, 365, 375 sodium borohydride, 416 sodium hexamethyldisilazide, 290 sodium hydride, 372, 375. 383 sodium in liquid ammonia, 440 sodium iodide, 379 sodium phenylselenide, 458 sodium trifluoroethoxide, 447 solid phase synthesis, 25 Sonogashira conditions, 409 Sonogashira coupling, 411 spartadienedione, 144 spontaneous csdodimerization, 23 S-shaped and C-shaped diastereomers, 83 stainless steel reactor, 283... [Pg.474]

Wuts and Sutherland [22] treated the allylic esters derived from pyran-2-car-boxylic acids with lithium hexamethyldisilazide (LHMDS) and allowed the enolate solution to warm up to room temperature when the enolates smoothly rearranged to give the products in good yield (Scheme 5.1.11). [Pg.216]