Improved addition of phenyllithium to hindered ketones by the use of non-polar media

Lecomte, Vincent; Stéphan, Elie; Jaouen, Gérard

doi:10.1016/s0040-4039(02)00597-x

Cited by 15 publications

(11 citation statements)

References 11 publications

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“…It was of interest to extend our studies to (−)-fenchone, which upon treatment with PhLi in Et 2 O gave (1 R ,2 R ,4 S )-2-phenyl fenchol ( 10 ). AM1 calculations of 10 show that the C2−C3 bond is longer than the C1−C2 bond, which is in agreement with X-ray crystallographic analyses of reported 2-arylfenchol derivatives .…”

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confidence: 99%

Stereo- and Regioselectivity in Dynamic Gas-Phase Thermoisomerization (DGPTI): Novel Route to α-Campholanic Acid and Derivatives

2003

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[reaction: see text] Dynamic gas-phase thermoisomerization (DGPTI) of (-)-2-phenylisoborneols effects stereo- and regioselective ring opening under formation of (+)-trans-alpha-campholanic acid derivatives. Similarly, (-)-alpha-2-phenylfenchol underwent under DGPTI conditions ring opening to (-)-fencholic acid derivatives. In both cases, DGPTI led to cleavage of the weakest bond in the isomeric bicyclic structures. A reaction mechanism involving a diradical intermediate is supported by a deuterium labeling study.

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confidence: 99%

Stereo- and Regioselectivity in Dynamic Gas-Phase Thermoisomerization (DGPTI): Novel Route to α-Campholanic Acid and Derivatives

2003

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“…The new quiral stannyl alcohols were obtained in good yields: 68-78%, i.e., similar to those reported for the addition of phenyllithium to (-)-menthone and other hindered cyclic ketones. 7 These reactions occur stereospecifically, leading in all cases to the alcohols resulting from the addition of the phenyl group to the less-hindered side of the carbonyl group (type 11 compounds). Our results confirm that the addition of phenyllithium to hindered ketones in nonpolar media can be achieved in good yields and with excellent selectivity.…”

Section: Methodsmentioning

confidence: 99%

“…Our results confirm that the addition of phenyllithium to hindered ketones in nonpolar media can be achieved in good yields and with excellent selectivity. 7 We then carried out the reduction of stannylketones 6a-6c with borane in THF in the presence of the Corey catalyst (S)-3,3-diphenyl-1-methyltetrahydro-3H-pyrrolo[1,2-c][1,3,2]oxazaborole. These reductions took place with good yields leading in all cases to mixtures of the two possible alcohols with d.e.…”

Section: Methodsmentioning

confidence: 99%

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Stereoselective addition of organotin anions to R-(+)-pulegone: a route to 8-triorganostannylmenthols

Dodero¹,

Giagante²,

Mandolesi³

et al. 2003

Arkivoc

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A study on the addition of trimethyl-, tri-n-butyl-, triphenyl-, and (-)-menthyldimethyltin lithium to (R)-(+)-pulegone (5) and (E)-benzalcyclohexanone (8) is reported. It was found that the conjugate addition of the organotin anions to 5 lead in the four cases to mixtures of two adducts in good yields (70-80%) and satisfactory diastereomeric excesses, d.e. (60-78%). The additions to 6 took place mostly in satisfactory yields (64-66%), but in very low yield in the case of the addition of (-)menthyldimethyltin lithium (23%); the d.e. were in the range of 36 to 100%. The addition of phenyl lithium in toluene to some of the new stannyl ketones led to the corresponding tertiary alcohols in fair yields (42-63%), and with d.e. of 40-100%. The reduction of some of the stannyl ketones with borane in THF catalyzed by a Corey catalyst gave the corresponding alcohols in ca 60% yield and with d.e. of 65%. Full 1 H-, 13 C-, and 119Sn-NMR data of the new organotins are given.

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“…[26] This phenylfenchol (5.16 g, 0.022 mol) was dissolved in THF (100 mL), the mixture was cooled to 0 8C, and n-butyllithium in hexanes (1.6 m, 0.022 mol) was added. Use of an excess of n-butyllithium, apparent from a change from yellow to orange, should be avoided due to unfavorable side products.…”

Section: Synthesis Of Diphenyl-((mentioning

confidence: 99%

Ligand Bite Governs Enantioselectivity: Electronic and Steric Control in Pd‐Catalyzed Allylic Alkylations by Modular Fenchyl Phosphinites (FENOPs)

Goldfuß

Löschmann²,

Röminger

2004

Chemistry A European J

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Modular fenchyl phosphinites (FENOPs) containing different aryl units-phenyl (1), 2-anisyl (2), or 2-pyridyl (3)-are efficiently accessible from (-)-fenchone. For comparison of the influence of the different aryl units on enantioselectivities and reactivities, these FENOPs were employed in Pd-catalyzed allylic alkylations. The strongly chelating character of P,N-bidentate 3 is apparent from X-ray structures with PdCl2 ([Pd3Cl2]), and with allyl-Pd units in ([Pd3(eta1-allyl)] and [Pd3(eta3-allyl)]). FENOP3 gives rise to a PdL* catalyst of moderate enantioselectivity (42 % ee, R product). Surprisingly, higher enantioselectivities are found for the hemilabile, monodentate FENOPs 1 (83 % ee, S enantiomer) and 2 (69 % ee, S enantiomer). Only small amounts of 1 or 2 generate selective PdL* catalysts, while complete abolition of enantioselectivity appears with unselective PdL*2 species with higher FENOP concentrations in the cases of 1 or 2. Computational transition structure analyses reveal steric and electronic origins of enantioselectivities. The nucleophile is electronically guided trans to phosphorus. endo-Allyl arrangements are favored over exo-allyl orientations for 1 and 2 due to Pd-pi-pyridyl interactions with short "side-on" Pd-aryl interactions. More remote "edge-on" Pd-pi-aryl interactions in 3 with Pd-N(lp) coordination favor endo-allyl units slightly more and explain the switch of enantioselectivity from 1 (S) and 2 (S) to 3 (R).

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Improved addition of phenyllithium to hindered ketones by the use of non-polar media

Cited by 15 publications

References 11 publications

Stereo- and Regioselectivity in Dynamic Gas-Phase Thermoisomerization (DGPTI): Novel Route to α-Campholanic Acid and Derivatives

Stereo- and Regioselectivity in Dynamic Gas-Phase Thermoisomerization (DGPTI): Novel Route to α-Campholanic Acid and Derivatives

Stereoselective addition of organotin anions to R-(+)-pulegone: a route to 8-triorganostannylmenthols

Ligand Bite Governs Enantioselectivity: Electronic and Steric Control in Pd‐Catalyzed Allylic Alkylations by Modular Fenchyl Phosphinites (FENOPs)

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