A simple, effective, new, palladium-catalyzed conversion of enol silanes to enones and enals

Larock, Richard C.; Hightower, Timothy R.; Kraus, George A.; Hahn, P.; Zheng, Deye

doi:10.1016/0040-4039(95)00306-w

Cited by 229 publications

(147 citation statements)

References 43 publications

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“…3,4 To a solution of sodium iodide (15.0 g, 100 mmol, 1.25 equiv) in ACN (125 mL) were added 2-ethylcyclohexanone (10.1 g, 80 mmol, 1.0 equiv), TEA (14.0 mL, 100 mmol, 1.25 equiv), and finally TMSCl (11.6 mL, 91.2 mmol, 1.14 equiv) in a dropwise fashion. After 1 h, pentane (75 mL) was added, the biphasic mixture was stirred for 2 min, and the pentane decanted.…”

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confidence: 99%

The Enantioselective Tsuji Allylation

2004

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Materials and Methods. Unless otherwise stated, reactions were performed in flame-dried glassware under an argon atmosphere using dry, deoxygenated solvents. Solvents were dried by passage through an activated alumina column under argon. Tetrabutylammonium triphenyldifluorosilicate (TBAT) was purchased from Sigma-Aldrich Chemical Company and azeotropically dried five times from acetonitrile prior to use. Trimethylsilyl chloride (TMSCl) and triethyl amine (TEA) were distilled from sodium hydride immediately prior to use. Sodium iodide was dried by heating at 90

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confidence: 99%

The Enantioselective Tsuji Allylation

2004

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“…For the introduction of the unsubstituted vinyl group, potassium vinyltrifluoroborate [18] (4n) was used conveniently. Dihydroquinone monoketal 1c [19] is another good substrate which undergoes the asymmetric 1,4-addition of arylboronic acids 2m-o with high enantioselectivity (96-98 % ee), although the chemical yields are a little lower (Scheme 2).…”

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confidence: 99%

Asymmetric 1,4‐Addition of Organoboron Reagents to Quinone Monoketals Catalyzed by a Chiral Diene/Rhodium Complex: A New Synthetic Route to Enantioenriched 2‐Aryltetralones

Tokunaga

Hayashi

2007

Adv Synth Catal

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A novel synthetic approach to 2-aryltetralones with high ee has been developed through asymmetric 1,4-addition of arylboronic acids to naphthoquinone monoketals catalyzed by a rhodium complex with the (R,R)-Ph-bod* ligand. The asymmetric addition proceeded in high yields with excellent enantioselectivity.Keywords: asymmetric catalysis; boron; chiral diene ligands; conjugate addition; quinone monoketals; rhodium Enantiomerically pure carbonyl compounds bearing aryl or alkenyl groups at the a position to the carbonyl moiety, which are represented by the 2-aryltetralones, constitute key intermediates to biologically important compounds.[1] Although their preparation using a stoichiometric amount of chiral reagents has been reported, [1,2] their catalytic asymmetric synthesis has not been well developed. The palladium-or nickel-catalyzed asymmetric a-arylation [3] and a-alkenylation [4] of carbonyl compounds provides an efficient method for the synthesis of chiral ketones substituted with quaternary stereogenic centers, but their application to the asymmetric synthesis of products containing hydrogen at the chiral carbon should present a problem due to the difficulty in keeping the stereogenic character of the chiral carbon center bound to an acidic hydrogen under basic conditions at a high reaction temperature. Another important method of providing a-chiral ketones is the catalytic asymmetric protonation of enolates, [5][6][7] but the asymmetric synthesis at the stage of carbon-carbon bond formation is more desirable. Our approach is to apply the rhodium-catalyzed asymmetric 1,4-addition [8,9] to the asymmetric synthesis of a-aryl ketones. Herein we report that the asymmetric 1,4-addition of aryl-and alkenylboron reagents to quinone monoketals [10] is efficiently catalyzed by a chiral diene/rhodium complex [11][12][13][14] and one of the enantioenriched addition products (96-99 % ee) is readily converted into a 2-aryltetralone without loss of enantiomeric purity.

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“…Data for 1 H NMR spectra are reported as follows: chemical shift (δ ppm) (multiplicity, coupling constant (Hz), integration). Data for 13 C NMR spectra are reported in terms of chemical shift relative to Me 4 Si (δ 0.0). IR spectra were recorded on a Perkin Elmer Paragon 1000 spectrometer and are reported in frequency of absorption (cm -1 ).…”

Section: The Arnold and Mabel Beckman Laboratories Of Chemical Synthementioning

confidence: 99%