Practical and robust method for stereoselective preparations of ketene silyl (thio)acetal derivatives and NaOH-catalyzed crossed-Claisen condensation between ketene silyl acetals and methyl esters

Asymmetric Total Syntheses of Two 3-Acyl-5,6- dihydro-2H-pyrones: (R)-Podoblastin-S and (R)- Lachnelluloic Acid with Verification of the Absolute Configuration of (−)-Lachnelluloic Acid

“…As depicted in Scheme 1 , our total synthesis started with the preparation of 1,3-bis(trimethylsiloxy)diene (Chan’s diene) 4 , which was obtained from ethyl acetoacetate in two steps in an 80% yield, according to the reported procedure [ 18 , 19 , 20 , 21 ]. Readily-accessible Soriente and Scettri’s Ti(O i Pr) 4 /( S )-BINOL‒catalyzed asymmetric Mukaiyama aldol addition of diene 4 with n CH 3 (CH 2 ) 2 CHO successfully produced the desired ( R )-δ-hydroxy-β-ketoester key intermediate 5 in an 82% yield with an excellent 98% ee (HPLC analysis, ESI).…”

Pyrethroid insecticides Chapter IVa. Reactivity of chrysanthemic acid and its lower esters

“…153 Another approach involves the sodium hydroxide catalyzed crossed-Claisen condensation of the ketene silyl acetal 55 with methyl cypermethrinate (1bMe) (Scheme 78). 171 It provides access, in excellent yield, to the betaketo ester 8'bc possessing a dimethyl-substituted alpha-carbon, a type of substructure usually difficult to synthesize. 171 Scheme 78.…”

“…171 It provides access, in excellent yield, to the betaketo ester 8'bc possessing a dimethyl-substituted alpha-carbon, a type of substructure usually difficult to synthesize. 171 Scheme 78. From methyl cypermethrinate to a related beta-keto ester involving ester silylenolates.…”

Preparation and Characterization of Urushiol Methylene Acetal Derivatives with Various Degrees of Unsaturation in Alkyl Side Chain

“…Derivatives. Catechol methylene acetal is an important pharmaceutical intermediate that is vital for the synthesis of quinolones; it is traditionally synthesized through a nucleophilic substitution reaction of catechol with methylene chloride under the catalytic action of NaOH [11]. Urushiol is a typical phenolic compound possessing a catechol structure and an alkyl side chain of 15 or 17 carbons [12]; it has two adjacent phenolic hydroxyl groups on the benzene ring, so a practical method for preparation of catechol methylene acetal is desirable for natural product synthesis and process chemistry of urushiol.…”