New Carbonyl Olefination Using Thioacetals

Protecting‐Group‐Free Total Synthesis of (E)‐ and (Z)‐Alstoscholarine

“…Finally, ethylidenation of 3 using Takedas reagent took place smoothly to provide the desired compound 15 (Scheme 5). [13] Due to the low stability of 15, it was submitted, after a rapid filtration of the reaction mixture, to VilsmeierHaack formylation conditions to afford (Z) and (E)-alstoscholarine (3:1 ratio) in 40 % yield over two steps. The two isomers were readily separated by preparative thin layer chromatography on silica gel (eluent: EtOAc/heptane = 1:4).…”

Synthesis of spiroacetals using functionalised titanium carbenoids

“…We have previously shown that using Takeda's procedure, 25 a range of functionalized titanium carbenoids 18 can be generated from easily prepared thioacetals.…”

The McMurry Coupling and Related Reactions

“…167 -169 Since thioacetals are readily prepared by the treatment of aldehydes and ketones with thiols in the presence of an appropriate acid catalyst and further derivatization of thioacetals, this method enjoys wide synthetic application (Eqs. 47, 170 48, 171 49, 170 50, 172 and 51. 173 Although the mixed-coupling readily proceeds with diphenyl thioacetals of aldehydes, the reaction using thioketals produces alkenes only when thioketals of sterically less-congested ketones such as acetone and cyclobutanone are employed.…”

“…52). 170 Thioacetals of alkynyl silyl ketones may also be subjected to coupling with carbonyl compounds (Eq. 53).…”

“…• (bath temp, 1.0 mmHg); 1 170 To a flask charged with finely powdered 4Å molecular sieves (200 mg), Mg turnings (58 mg, 2.4 mmol), and Cp 2 TiCl 2 (498 mg, 2 mmol) were added THF (4 mL) and P(OEt) 3 (0.68 mL, 4 mmol) with stirring at rt under Ar. After 3 h, a solution of α,α-bis(phenylthio) toluene (175) (170 mg, 0.55 mmol) in THF (1 mL) was added to the THF solution of the resulting Cp 2 Ti[P(OEt) 3 ] 2 and the reaction mixture was further stirred for 5 min.…”