Metal-alkene π-chelation: A stereodirecting effect in allylzincation reactions and in zinc mediated cyclopropanations

Marek, Ilane; Beruben, Dov; Normant, Jean F.

doi:10.1016/0040-4039(95)00614-i

Cited by 42 publications

(18 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Two scenarios can be imagined, however. The interaction of Zn(II) with unsaturated π-systems has been indicated in the control of stereoselective reactions 61,62. Furthermore, we have recently observed π-interactions between Zn(II) and a C–C double bond in the solid state,63 Bochmann and coworkers have characterized η2-binding of toluene to Zn(C 6 F 5 ) 2 in the solid state,64,65 and Vigalok and coworkers presented solid state and solution evidence for Zn(II) interactions with alkyne π-systems 66.…”

Section: Resultsmentioning

confidence: 99%

Highly Enantio- and Diastereoselective One-Pot Methods for the Synthesis of Halocyclopropyl Alcohols

et al. 2008

View full text Add to dashboard Cite

The lack of methods for the stereoselective transfer of functionalized carbenoids is one of the most significant deficiencies of Simmons–Smith cyclopropanation reactions. Outlined herein are one-pot methods for the catalytic asymmetric synthesis of halocyclopropyl alcohols with up to four stereogenic centers from achiral starting materials. The first method involves asymmetric alkyl addition to a conjugated enal to generate an allylic alkoxide followed by tandem diastereoselective iodo-, bromo- or chlorocyclopropanation to furnish halocyclopropyl alcohols. Enantioselectivities in these processes range from 89–99% and dr > 20:1 were achieved with all substrates optimized. The second method consists of an asymmetric vinylation of a saturated or aromatic aldehyde followed by a diastereoselective iodocyclopropanation to produce iodocyclopropyl alcohols with enantioselectivities between 86 and 99% and dr > 20:1. These complementary methods enable the efficient synthesis of a variety of halocyclopropyl alcohols in one-pot procedures. Preliminary efforts to functionalize iodocyclopropanes involve reaction with an excess of LiCu(n-Bu)2 to generate the cyclopropyl cuprate. This intermediate can be quenched with allyl bromides to generate the allylated cyclopropyl alcohols without loss of enantio- or diastereoselectivity.

show abstract

Section: Resultsmentioning

confidence: 99%

Highly Enantio- and Diastereoselective One-Pot Methods for the Synthesis of Halocyclopropyl Alcohols

et al. 2008

View full text Add to dashboard Cite

show abstract

“…The dramatic effects of conjugated enynes on reactivity and regioselectivity are not consistent with a purely steric and/or electronic phenomenon. Tethered alkenyl groups in enynes and dienes are also known to increase the reactivity and regioselectivity of transition metal-catalyzed coupling reactions 11. The directing effects of tethered alkenyl groups are usually explained by coordination with the metal center during the rate- and regioselectivity-determining step, since the length of tether has dramatic effects on the reactivity and regioselectivity of enynes.…”

Section: Introductionmentioning

confidence: 99%

Origins of Regioselectivity and Alkene-Directing Effects in Nickel-Catalyzed Reductive Couplings of Alkynes and Aldehydes

et al. 2010

View full text Add to dashboard Cite

Origins of regioselectivity and alkene-directing effects in nickel-catalyzed reductive coupling reactions were investigated by density functional calculations. Regioselectivity of simple alkynes is controlled by steric effects, while conjugated enynes and diynes are predicted to have increased reactivity and very high regioselectivities, placing alkenyl or alkynyl groups distal to the forming C–C bond. The reactions of enynes and diynes involve 1,4-attack on the conjugated enyne of the Ni-carbonyl complex on the conjugated enyne or diyne.

show abstract

“…58,59 One such example is the allylzincation reaction shown in Scheme 1. 58, 59 The high degree of acyclic stereocontrol observed was explained by coordination of the pendent olefin to zinc.…”

Section: Introductionmentioning

confidence: 99%

Unprecedented Alkene Complex of Zinc(II): Structures and Bonding of Divinylzinc Complexes

et al. 2006

View full text Add to dashboard Cite

This report describes the solid state structures of a series of divinylzinc complexes, one of which represents the only structurally characterized zinc(II) π-complex. Vinylzinc reagents, Zn[C(Me) =CH 2 ] 2 (1) and Zn[C(H)=CMe 2 ] 2 (2), have been synthesized and isolated as white crystalline solids in 66% and 72% yield, respectively. Each compound exhibits an infinite polymeric architecture in the solid state via a series of zinc-π (1) and zinc-σ-bonded (2)

show abstract

Metal-alkene π-chelation: A stereodirecting effect in allylzincation reactions and in zinc mediated cyclopropanations

Cited by 42 publications

References 23 publications

Highly Enantio- and Diastereoselective One-Pot Methods for the Synthesis of Halocyclopropyl Alcohols

Highly Enantio- and Diastereoselective One-Pot Methods for the Synthesis of Halocyclopropyl Alcohols

Origins of Regioselectivity and Alkene-Directing Effects in Nickel-Catalyzed Reductive Couplings of Alkynes and Aldehydes

Unprecedented Alkene Complex of Zinc(II): Structures and Bonding of Divinylzinc Complexes

Contact Info

Product

Resources

About