Regioselectivity of Addition of Organolithium Reagents to Enones:  The Role of HMPA

Reich, Hans J.; Sikorski, William H.

doi:10.1021/jo981765g

Cited by 71 publications

(27 citation statements)

References 22 publications

(19 reference statements)

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“…[8] The most frequently used methods for structure elucidation of organolithium species have been single-crystal structure analysis and high-resolution as well as solid-state NMR spectroscopy. [9] In many mechanistic studies the reactivity or selectivity was found to strongly depend on the aggregates, [10] which in the case of lithiumamides and organolithiums are assumed to be mainly monomers, dimers, open dimers, and SSIPs. [11] This underlines the importance of accurate structure elucidation to adequately tune reaction conditions and thereby also reaction pathways.…”

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confidence: 99%

Characterization of a Multicomponent Lithium Lithiate from a Combined X‐Ray Diffraction, NMR Spectroscopy, and Computational Approach

et al. 2014

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An unusual lithium lithiate [Li(diglyme)2][(diglyme)Li2(C4H3S)3], made up from three carbanions, two lithium cations, and a single donor base molecule in the anion and a single lithium cation, coordinated by two donor base molecules, is investigated in a combined study including X-ray diffraction, NMR spectroscopy and computational approaches in solution and the solid state. While the multicomponent lithiate is the only species present in the solid state, solution NMR spectroscopy and computational methods were employed to identify a second species in solution. The dimer [(diglyme)Li(C4H3S)]2 coexists with the lithiate in solution in a 1:1 ratio, the more the higher the polarity of the solvent is. Only the combination of this multitude of methods provides a firm picture of the whole.

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confidence: 99%

Characterization of a Multicomponent Lithium Lithiate from a Combined X‐Ray Diffraction, NMR Spectroscopy, and Computational Approach

et al. 2014

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“…In the absence of HMPA, the yields of the desired products were rather low (<10%). HMPA is a highly polar and aprotic solvent, and is frequently used to accelerate organolithium reactions [13]. In this reaction, the role of HMPA may be to promote the phosphoryl-stabilized carbanions 2 to react much more easily with acrylonitrile, and indeed the Michael addition adducts 3 were obtained in high yields.…”

Section: Resultsmentioning

confidence: 99%

“One‐pot” synthesis of (Z)‐2‐aryl‐1‐(2‐cyanoethyl)ethenylphosphonates via hexamethylphosphoramide‐promoted sequential transformation

Wang

Shen

2002

Heteroatom Chemistry

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“…While conjugate addition to α,β-unsaturated carbonyl compounds is generally affected by soft organometallics (Cu, Ni, etc. ), use of organolithium reagents for that purpose has long been a chal- [6]. Remarkable 1,4-selectivities were reported for the addition of organolithium compounds to substituted cyclohexenones and linear ketones in the presence of MAD 1 [7] or the structurally related aluminum tris(2,6-diphenylphenoxide) [8].…”

Section: Methodsmentioning

confidence: 99%

Methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD)

Pohnert

1999

J. prakt. Chem.

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Bulky designer aluminum Lewis acids of type 1 [1], first introduced into organic synthesis by Yamamoto and coworkers [2], provide remarkably versatile reagents for the control of regio-, stereo-and chemoselective transformations. The first described compound of this class, methylaluminum bis(2,6di-tert-butyl-4-methylphenoxide) (MAD) 1 proved to be a universal tool for the selective promotion of carbon-carbon bond formation, radical or pericyclic reactions. The reagent is readily available in a large scale from low cost commercial precursors [2].In general, use of MAD 1 gives good to excellent selectivities and yields but, if required, screening of related reagents like 5, 6 or even more bulky aluminium complexes with three phenolic substituents may result in improved results [4].

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Regioselectivity of Addition of Organolithium Reagents to Enones: The Role of HMPA

Cited by 71 publications

References 22 publications

Characterization of a Multicomponent Lithium Lithiate from a Combined X‐Ray Diffraction, NMR Spectroscopy, and Computational Approach

Characterization of a Multicomponent Lithium Lithiate from a Combined X‐Ray Diffraction, NMR Spectroscopy, and Computational Approach

“One‐pot” synthesis of (Z)‐2‐aryl‐1‐(2‐cyanoethyl)ethenylphosphonates via hexamethylphosphoramide‐promoted sequential transformation

Methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD)

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