Glyoxylate-ene Reaction Research Articles

Novel approach to A-ring synthon for Pd-catalyzed synthesis of 1α-hydroxylated vitamin D metabolites

A novel approach to an A-ring synthon for Pd-catalyzed synthesis of 1α-hydroxylated vitamin D metabolites is described. Key step is an asymmetric glyoxylate ene reaction to access a highly diastereomerically pure α-hydroxy ester. Subsequent stereospecific transformation to an anti-1,3-diol and appropriate chemical modifications at both ends of the acyclic precursor leads to a diastereomerically and enantiomerically pure silylated anti-1,3-diol enyne, serving as a versatile A-ring synthon for its use in vitamin D synthesis.

Ene reactions of 2-borylated α-methylstyrenes: a practical route to 4-methylenechromanes and derivatives.

4-Methylenechromanes were prepared via a three-step process from 2-borylated α-methylstyrenes. This sequence is based on a key glyoxylate-ene reaction catalyzed by scandium(iii) triflate. The resulting γ-hydroxy boronates, which cyclise to seven-membered homologues of benzoxaborole on silica gel, were cleanly oxidized with sodium perborate, and then cyclised under Mitsunobu conditions. Additionally, several further functional transformations of 4-methylenechromanes or their precursors were carried out to illustrate the synthetic potential of these intermediates.

ChemInform Abstract: Highly Enantioselective and anti‐Diastereoselective Catalytic Intermolecular Glyoxylate—Ene Reactions: Effect of the Geometrical Isomers of Alkenes.

AbstractAn efficient method for the highly dia‐ and enantioselective synthesis of anti‐homoallylic alcohols via an In(III)‐catalyzed intermolecular glyoxylate‐ene reaction is developed.

Highly enantioselective and anti-diastereoselective catalytic intermolecular glyoxylate-ene reactions: effect of the geometrical isomers of alkenes.

An efficient method for the synthesis of homoallylic alcohols with high enantioselectivities and anti-diastereoselectivities via an In(III)-catalyzed intermolecular glyoxylate-ene reaction has been developed. The geometrical isomers of alkenes were shown to have different reactivities. Only the isomers of the alkenes having a proton β-cis to the substituent reacted in this catalytic system.

Enhanced reactivity and enantioselectivity in catalytic glyoxylate-ene reactions using chiral bis(oxazoline)–copper complex in an ionic liquid

An optimal hydrophobic ionic liquid was discovered as a solvent for highly enantioselective glyoxylate-ene reactions catalyzed by a chiral bis(oxazoline)–copper complex. The reactivity and stereoselectivity were highly dependent upon the property of the ionic liquids; reactions between olefins and ethyl glyoxylate in [Bmim]SbF6 at ambient temperature provided remarkably enhanced reactivity and stereoselectivity, which greatly exceed those of the corresponding reactions in dichloromethane. Furthermore, the metal–ligand complex was readily recycled up to eight times while exhibiting no significant decrease in reaction efficiency.

ChemInform Abstract: Highly Regio- and Stereocontrolled Glyoxylate-Ene Reaction with (Homo)- Allylic Ethers: Remarkable Alkoxy Effect in Regio- and Stereocontrol.

A highly regio- and sterecontrolled glyoxylate-ene reaction with allylic and homoallylic ethers has been developed, which allows regio- and stereospecific multifunctionalizations as highlighted by a short synthesis of (±)-avenaciolide

ChemInform Abstract: Chiral Titanium Complex Catalyzed Carbonyl-Ene Reaction with Glyoxylate: Remarkable Positive Nonlinear Effect.

Abstract The enantioselective glyoxylate-ene reaction catalyzed by chiral titanium complex derived from partially resolved binaphthol (BINOL) is shown to exhibit a remarkable level of asymmetric amplification (positive nonlinear effect). Thus, the optical yield of the ene product significantly exceeds the enantio-purity of the chiral ligand (BINOL).

ChemInform Abstract: Synthesis of Optically Active Bicyclic Lactone Building Blocks Using Catalytic Enantioselective Glyoxylate-ene Reaction.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Recyclable copper catalysts in the enantioselective glyoxylate-ene reaction catalyzed by chiral fluorous-tagged bis(oxazolines)

Chiral fluorous bis(oxazoline)/copper complexes have been applied to the asymmetric glyoxylate-ene reaction, giving moderate to high enantioselectivities. An efficient separation of the copper catalyst using a solid/liquid separation or the FRPSG concept, and its reuse was achieved.

Enantioselective Glyoxylate‐ene Reaction Using a Novel Spiro Bis(isoxazoline) Ligand in Copper Catalysis.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Asymmetric Glyoxylate-Ene Reactions Catalyzed by Chiral Pd(II) Complexes in the Ionic Liquid [bmim][PF6

The room temperature ionic liquid [bmim][PF6] was employed as the reactionmedium in the asymmetric glyoxylate-ene reaction of α-methyl styrene (4a) with ethylglyoxylate using chiral palladium(II) complexes as the catalysts. [Pd(S-BINAP)(3,5-CF3-PhCN)2](SbF6)2 (1b) showed the highest catalytic activity. Under the reaction conditionsof 40 oC, 0.5 h, and 1b/4a molar ratio of 0.05, ethyl α-hydroxy-4-phenyl-4-pentenoate wasobtained in excellent chemical yield (94 %) with high enantioselectivity (70 %). Otherα-hydroxy esters can also be obtained in high chemical yields and enantioselectitiesthrough the glyoxylate-ene reactions of alkenes with glyoxylates catalyzed by 1b in[bmim][PF6]. Moreover, the ionic liquid [bmim][PF6] which contained the palladium(II)complex could be recycled and reused several times without significant loss of the catalyticactivity.

Enantioselective glyoxylate-ene reaction using a novel spiro bis(isoxazoline) ligand in copper catalysis

Novel chiral spiro bis(isoxazoline) ligands 3 and 4 are synthesized from an optically active olefin. The Cu(II)-spiro bis(isoxazoline) complex prepared in situ from Cu(OTf) 2 and 3 promoted the glyoxylate-ene reaction in high yield and moderate enantioselectivity (up to 70%).

Enantioselective glyoxylate-ene reactions catalysed by (salen)chromium(III) complexes

An enantioselective carbonyl-ene reaction of alkyl glyoxylates with various 1,1-disubstituted olefins, catalysed by chiral (salen)Cr(III)BF 4 complexes, has been studied. We found that a chromium complex bearing adamantyl substituents at the 3,3′-positions of the salicylidene moiety catalysed the reaction with much greater selectively than the classic Jacobsen-type catalyst. The reaction proceeded effectively under undemanding conditions in the presence of 2 mol % of the catalyst in an acceptable yield and with 59–92% ee.

Modification of alkoxo ligands of BINOL–Ti ladder: Isolation and X-ray crystallographic analysis

The stable binaphthol–titanium ladder complexes have been successfully prepared by using bulky alkoxo ligands. From the secondary OR ligand (cyclohexyloxo, 2,4-dimethyl-3-pentyloxo or 2-adamantyloxo) and terially OR ligand ( tert-butyloxo, 1-adamantyloxo), partial hydrolysis proceeded to give the μ 3-oxo titanium complexes. The use of [Ti(BINOLato)(OEt) 2] n made it possible to prepare the Ti(BINOLato)(OR) 2 complexes using alcohols (ROH) of high boiling point (R = cyclohexyl, 2-adamantyl, 1-adamantyl). X-ray analyses of [( R)-1,1′-bi-2-naphtholato]bis(O-2,4-dimethyl-3-pentyloxo)titanium and [( R)-3,3′-dimethyl-1,1′-bi-2-naphtholato]bis(2-adamantyloxo)titanium showed a good agreement with the estimated ladder complexes. The catalytic activity of BINOL–Ti catalyst analogues, obtained by partial hydrolysis of Ti(BINOLato)(OR) 2 with wet MS 4A was studied in asymmetric glyoxylate-ene reaction by two methods. Moderate to good chemical yields and enantioselectivities were obtained.

Synthesis of α-Hydroxy Esters by Glyoxylate-Ene Reaction in Lewis Acid Chloroaluminate Ionic Liquids

Abstract The chloroaluminate ionic liquid composed of AlCl 3 and 1-butyl-3-methylimidazolium chloride ([bmim]Cl) was used as the solvent and catalyst to synthesize α-hydroxy esters from alkene and glyoxylate via the glyoxylate-ene reaction. Under the reaction conditions of 15°C, 4 h, and AlCl 3 /[bmim]Cl molar ratio of 2, the ethyl α-hydroxy-4-phenyl-4-pentenoate with a high yield of 95.2% is obtained in the reaction of reaction of α-methyl styrene and ethyl glyoxylate. Other α-hydroxy esters can also be obtained in high yields through the glyoxylate-ene reaction. Moreover, the chloroaluminate ionic liquid can be reused several times.

An efficient direct activation method transferring diastereopure platinum complex of BIPHEP to highly efficient Lewis acid catalyst for enantioselective carbonyl-ene reaction

An efficient direct activation method was developed to transfer diastereopure λ-[(BIPHEP)Pt( S-BINOL)] to highly active and selective enantiopure Lewis acid λ-[(BIPHEP)Pt](SbF 6) 2 by silver hexafluoroantimonate(AgSbF 6) for the enantioselective carbonyl-ene reactions. Both enantioselective glyoxylate-ene reactions between ethyl glyoxylate and alkenes, and enantioselective carbonyl-ene reactions between phenylglyoxal and alkenes were studied demonstrating good catalytic activity and enantioselectivity. Particularly, for the enantioselective carbonyl-ene reaction between phenylglyoxal and 2,3-dimethyl-1-butene, the Lewis acid catalyst λ-[(BIPHEP)Pt](SbF 6) 2 generated with this direct activation method by silver hexafluoroantimonate(AgSbF 6) could give excellent ee values high up to 94%.

Enantioselective turnover in glyoxylate-ene reactions catalyzed by chiral copper complexes

The catalytic, enantioselective carbonyl-ene reaction of ethyl glyoxylate with α-methylstyrene and 4-halo-α-methylstyrene has been investigated in the presence of copper triflate–bisoxazoline complexes. The reaction proceeded smoothly to give γ,δ-unsaturated-α-hydroxy esters in moderate to good yields and with excellent enantioselectivity (up to 100% ee). A hypothesis has been provided to explain the reversal of enantioselectivity in the reaction.

An Efficient Diastereoselective Glyoxylate‐ene Reaction Using N‐Glyoxyloyl Camphorpyrazolidinone as an Enophile.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Insoluble Polystyrene-Bound Bis(oxazoline): Batch and Continuous-Flow Heterogeneous Enantioselective Glyoxylate?Ene Reaction.

Abstract The use of a new, insoluble polymer-bound bis(oxazoline) ligand (IPB–box) for the copper-catalyzed heterogeneous enantioselective glyoxylate–ene reaction is described. Good activity and ee values in the range 85–95% have been obtained during five to seven recycles, either in batch mode or under flow conditions, demonstrating also the recovery and reuse of the whole catalytically active copper complex.

An efficient diastereoselective glyoxylate-ene reaction using N-glyoxyloyl camphorpyrazolidinone as an enophile

The diastereoselective glyoxylate-ene reaction of N-glyoxyloyl camphorpyrazolidinone ( 1 ) with various alkenes 2a– g in the presence of Lewis acid is described. The corresponding α-hydroxyl carbonyls were generally obtained in moderate to high chemical yields (64–87%) and with high levels of diastereoselectivities (up to 94% de). The predominance of products with the S absolute configuration at the newly formed stereogenic center was established by single crystal X-ray analysis and the importance of stereochemical induction is discussed.