The direct catalytic asymmetric aldol reaction of α-substituted nitroacetates with aqueous formaldehyde under base-free neutral phase-transfer conditions

Enantioselective direct aldol reaction of α-substituted nitroacetates with aqueous formaldehyde for the synthesis of α-alkyl serines has been achieved under base-free neutral phase-transfer conditions with a bifunctional chiral phase-transfer catalyst.     

Organocatalytic asymmetric conjugate addition of α-substituted cyanoacetates to maleimides

The asymmetric conjugate addition of α-substituted cyanoacetates to N-substituted maleimides has been developed. A number of cinchona alkaloids and amine thioureas were evaluated as catalysts. Takemoto’s catalyst was found to be the most efficient for the transformation. Chiral succinimides with two adjacent quaternary and tertiary stereogenic carbon centers were obtained in good yields, enantioselectivities, and diastereoselectivities. The products were converted to chiral γ-lactams conveniently without a loss in the enantioselectivity.     

Chiral squaramides catalyzed diastereo- and enantioselective Michael addition of α-substituted isocyanoacetates to N-aryl maleimides

An efficient diastereo- and enantioselective Michael addition of α-substituted isocyanoacetates to N-aryl maleimides catalyzed by quinine or cyclohexane-1,2-diamine derived squaramide catalysts has been disclosed, affording the corresponding adducts in good yields (up to 99%), high diastereoselectivities (up to >20:1 dr) and good to excellent enantioselectivities (up to 94% ee) under mild conditions.     

Hydroxymethylation of α-substituted nitroacetates

Only 1 mol % of K₃PO₄ is efficient enough to catalyze the hydroxymethylation of α-substituted nitroacetates in good to excellent yield. Both aliphatic and aryl substituted nitroacetates work well under this reaction. The first catalytic asymmetric version of this reaction also reported that 10 mol % of cupreidine could catalyze this reaction up to 71% ee and 89% yield. Paraformaldehyde and formalin could both serve as the hydroxymethylation C1 unit. The synthetic application of products is also demonstrated.     

Catalytic enantioselective conjugate addition of indoles to simple α,β-unsaturated ketones

Chiral [Al(salen)Cl] complex (10 mol%) in the presence of 2,6-lutidine (10 mol%) was found to be effective in catalysing the enantioselective Friedel-Crafts-type conjugate addition of indoles (3) to (E)-arylcrotyl ketones (2), furnishing the corresponding β-indolyl ketones in excellent yield and high enantioselectivity (ee up to 89%).     

Practical asymmetric synthesis of α-methylserine derivatives under mild phase-transfer conditions

The enantioselective methylation reaction of phenyloxazoline tert-butyl ester 5 using (R)-4b as a catalyst under mild phase-transfer conditions provides optically active α-methylserine derivatives in moderate yields with high enantioselectivity. Other α-alkylated serine derivatives are also achievable in high yields with high enantioselectivity by using catalytic amount of (R)-4b.     

Highly diastereo- and enantioselective organocatalytic michael addition of α-ketoamides to nitroalkenes

The first organocatalytic enantio- and diastereoselective conjugate addition of α-ketoamides to nitroalkenes has been achieved using a bifunctional amino thiourea catalyst. In this new approach, the substrate amide proton plays a critical role in the formation of the Michael anti-adducts in high yields and high stereoselectivities. To illustrate the high synthetic potential of this methodology, the diastereo- and enantioselective synthesis of a hexasubstituted cyclohexane via a Michael-Michael-Henry cascade reaction is described.     

Asymmetric Michael addition of α-substituted isocyanoacetates with maleimides catalyzed by chiral tertiary amine thiourea

A highly diastereoselective and enantioselective Michael addition of α-substituted isocyanoacetates with maleimides catalyzed by bifunctional tertiary amine thioureas has been developed. Various chiral succinimide derivatives bearing adjacent quaternary and tertiary stereocenters were prepared in excellent yields (up to 98%), diastereoselectivities (up to 99:1), and enantioselectivities (up to 98% ee). The synthetic utility of chiral succinimide derivatives is also demonstrated in the preparation of h5-HT(1d) receptor agonist motifs.     

Regio- and enantioselective conjugate addition of β-nitro α,β-unsaturated carbonyls to construct 3-alkenyl disubstituted oxindoles

Reversal of regioselectivity in the catalytic asymmetric conjugate additions of 3-substituted oxindoles to β-nitroenones or β-nitroacrylates was established with chiral scandium catalysts. It enabled the construction of functionalized 3,3-disubstituted oxindoles, including terminal and internal vinyl groups in excellent yields and ee values.     

Alkylation of cyclododecanone with α,ω-dibromoalkanes under conditions of phase-transfer catalysis

Alkylation of cyclododecanone with ,-dibromoalkanes Br(CH) _n Br (n=3, 4, 5) under conditions of phase-transfer catalysis in the presence of KOH results in the formation of either bicyclic ketones forn=3 and 5 or a mixture of bicyclic and spirocyclic ketones forn=4.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1436–1438, August, 1994.     

Asymmetric synthesis of α,β-substituted γ-amino acids via conjugate addition

The first conjugate addition reaction of organocuprates to N-enoyl oxazolidinone where a N-protected γ-nitrogen atom and an α-methyl group are present into α, β-unsaturated system is described. This reaction gave anti-products in moderate yields and high diastereomeric ratios. The anti-products have two contiguous stereogenic centers, one formed by the conjugate addition reaction and the other by a diastereoselective protonation reaction. The removal of chiral oxazolidinone moiety and N-deprotection of amino group furnished chiral α, β-disubstituted γ-amino acids.     

Highly enantioselective Michael addition of α,α-disubstituted aldehydes to maleimides catalyzed by new primary amine-squaramide bifunctional organocatalysts

New bifunctional primary amine-squaramides catalyzed asymmetric Michael addition reaction of α,α-disubstituted aldehydes to maleimides has been developed. This organocatalytic asymmetric reaction provides easy access to functionalized succinimides with a broad substrate scope. Both enantiomers of desired succinimide derivatives were obtained in good to excellent yields (up to 98%) with excellent enantioselectivities (up to >99%?ee).     

Enantioselective synthesis of quaternary α-aminophosphonates via conjugate addition of α-nitrophosphonates to enones

Enantioselective Michael addition of α-nitrophosphonates to enones for the synthesis of α-aminophosphonates is reported for the first time. The reaction proceeds in good to high yields and moderate to high selectivity in the presence of a new quinine thiourea catalyst. The quaternary nitrophosphonates were conveniently transformed to cyclic quaternary α-aminophosphonates via in situ reduction-intramolecular cyclization or Baeyer-Villiger oxidation followed by in situ reduction-intramolecular cyclization.     

Palladium-catalyzed asymmetric conjugate addition of arylboronic acids to five-, six-, and seven-membered β-substituted cyclic enones: enantioselective construction of all-carbon quaternary stereocenters

The first enantioselective Pd-catalyzed construction of all-carbon quaternary stereocenters via 1,4-addition of arylboronic acids to β-substituted cyclic enones is reported. Reaction of a wide range of arylboronic acids and cyclic enones using a catalyst prepared from Pd(OCOCF(3))(2) and a chiral pyridinooxazoline ligand yields enantioenriched products bearing benzylic stereocenters. Notably, this transformation is tolerant to air and moisture, providing a practical and operationally simple method of synthesizing enantioenriched all-carbon quaternary stereocenters.     

Cobalt-catalyzed conjugate addition of silylacetylenes to α,β-unsaturated ketones

Catalytic addition of silylacetylenes to α,β-unsaturated ketones proceeded in the presence of a cobalt complex coordinated with a bisphosphine ligand to give high yields of β-alkynylketones.     

Sc(III)-catalyzed enantioselective addition of thiols to α,β-unsaturated ketones in neutral water

This report concerns Lewis acid catalyzed enantioselective sulfa-Michael addition in neutral water by using a very efficient Sc(OTf)(3)/bipyridine 1 catalytic system. It is noteworthy that the protocol presented employs water as a reaction medium and allows us to obtain very high stereoselectivity and satisfactory yields for β-keto sulphides deriving from aliphatic thiols. The recovery and reuse of both the aqueous medium and the catalytic system is also reported.     

Organocatalytic synthesis of quaternary stereocenter bearing a fluorine atom: enantioselective conjugate addition of α-fluoro-β-ketoesters to nitroalkenes

The catalytic enantioselective conjugate addition reaction of α-fluoro-β-ketoesters to nitroalkenes promoted by chiral bifunctional organocatalysts is described. The treatment of α-fluoro-β-ketoesters with nitroalkenes under mild reaction conditions afforded the corresponding Michael adducts containing a fluorinated quaternary stereogenic center with excellent enantioselectivity (up to >99% ee).     

The synthesis and stereoselective conjugate addition reactions of α-alkoxyorganocuprate reagents

α-Alkoxyorganocuprate reagents have been prepared from α-alkoxyorganostannanes. The cuprates undergo diastereoselective conjugate addition reactions with cyclohexenone with up to 8:92 selectivity. The effects of trimethylsilyl chloride on the chemical yields and the diastereoselectivity of the reaction are described.