The domino reaction of enamines, electrophiles (N-sulfonylimines, N-tosylisocyanate, or diethyl azodicarboxylate), and trichlorosilane provided trans-amines (trans/cis = > 99:1 to 96:4). Meanwhile, the sequential imino ene-type reaction of enamines and electrophiles/NaBH3CN reduction afforded cis-amines (trans/cis = 1:>99 to 15:85). The reversal of selectivity is discussed on the basis of diastereofacial selection of the plausible iminium ion intermediates. For the domino reaction of cyclic enamines and cyclic imines, high enantioselectivity (er = 95.7:4.3 to 99.9:0.1) was achieved by utilizing chiral Lewis base catalysts.

TiCl4-promoted aldol reaction of ketones as aldol acceptors followed by elimination of the titanoxy group from the Ti-aldolates affords β,β-disubstituted α,β-unsaturated carbonyl compounds in a one-pot procedure. The use of additives, such as DMF, N,N,N′,N′-tetramethylethylenediamine, and pyridine, in the elimination step was found to be important.

Enantioselective conjugate addition of styrylboronic acid to dienones was effectively catalyzed by an O-monoacyltartaric acid to afford monostyrylated products with good enantioselectivity. The RCM of the monostyrylated products using the Hoveyda–Grubbs II catalyst afforded optically active cyclopentenones, including a synthetic intermediate of the antitumor agent TEI-9826. The study shows that a diene additive such as 1,6-heptadiene or diallyl ether was essential for the RCM.

Enamines react rapidly with N-sulfonylimines to afford imino ene-type adducts. The reaction proceeds even at −78 °C in the presence of acetic acid and shows high diastereoselectivity. Acid hydrolysis of imino ene-type products affords β-amino ketones, and reduction with NaBH3CN furnishes N-sulfonyl-1,3-diamines with high diastereoselectivities. The stereochemistry of these transformations is considered based on transition state models.

In this study, we report a new highly diastereoselective domino reaction of imines, enamines, and trichlorosilane. The reaction involves CC bond formation between the imine and enamine followed by the intramolecular reduction of the resulting iminium intermediate by the hydrosilyl group, affording a 1,2-anti-2,3-anti-1,3-diamine in good yield with high diastereoselectivity. Lewis base catalysts such as HMPA increased the chemical yield without decreasing the diastereoselectivity.

DFT calculations suggest that O-monoacyl l-tartaric acids catalyze the asymmetric conjugate alkenylboration of enones through transition structures that are stabilized by hydrogen-bonding interactions. Formation of a five-membered acyloxyborane is proposed. The hydrogen of the free carboxy group derived from the catalyst interacts with the carbonyl group of the cyclic acyloxyborane, stabilizing the transition structure and reducing the flexibility of the system. Additional stabilizing nonclassical CH···O hydrogen-bond interactions seem to determine the observed enantioselectivity.

Treatment of an optically pure tartaric acid-derived diiodide and various secondary phosphine oxides with LHMDS provides the corresponding aryl group-modified DIOP dioxides (Ar-DIOPOs). The activities of Ar-DIOPOs as Lewis base catalysts were investigated for several asymmetric transformations using chlorosilane reagents. The p-tolyl-substituted DIOPO (p-tolyl-DIOPO) was most effective for the reductive aldol reaction of chalcone and aldehydes with trichlorosilane, whereas the 2,8-dimethylphenoxaphosphine-derived DIOPO (DMPP-DIOPO) afforded the best enantioselectivity for the phosphonylation of conjugated aldehydes and the chlorinative aldol reaction of an ynone and benzaldehyde.

We have found that O-monoacyltartaric acids catalyze asymmetric conjugate addition of boronic acids to enones with good enantioselectivity, and the 3,5-di(tert-butyl)benzoyl group provides the best results among the acyl groups examined.

Chiral dinitrones were synthesized by the condensation of a C2-symmetrical chiral dihydroxylamine with various aldehydes. The electronic and steric properties of the dinitrones can be modified by changing the aldehyde component. The activity of dinitrones as Lewis base catalysts was examined for the asymmetric allylation of aldehydes with allyltrichlorosilanes. Using DMPU as an additive in chloroform, the reaction proceeded at room temperature to afford allylated products in good yields and good enantioselectivities.(1S,2S,NZ,N′Z)-N,N′-Dibenzylidenecyclohexane-1,2-diamine N,N′-dioxideC20H22N2O2[α]D30=+279.8 (c 1.0, CHCl3)Source of chirality: (S,S)-1,2-cyclohaxanediamineAbsolute configuration: (1S,2S)(1S,2S,NZ,N′Z)-N,N′-Bis(naphthalene-1-ylmethylene)cyclohexane-1,2-diamine N,N′-dioxideC28H26N2O2[α]D22=-56.6 (c 1.0, CHCl3)Source of chirality: (S,S)-1,2-cyclohaxanediamineAbsolute configuration: (1S,2S)(1S,2S,NZ,N′Z)-N,N′-Bis(naphthalene-2-ylmethylene)cyclohexane-1,2-diamine N,N′-dioxideC28H26N2O2[α]D19=+578.6 (c 1.0, CHCl3)Source of chirality: (S,S)-1,2-cyclohaxanediamineAbsolute configuration: (1S,2S)(1S,2S,NZ,N′Z)-N,N′-Bis(4-chlorobenzylidene)cyclohexane-1,2-diamine N,N′-dioxideC20H20Cl2N2O2[α]D31=+223.6 (c 1.0, CHCl3)Source of chirality: (S,S)-1,2-cyclohaxanediamineAbsolute configuration: (1S,2S)(1S,2S,NZ,N′Z)-N,N′-Bis(4-nitrobenzylidine)cyclohexane-1,2-diamine N,N′-dioxideC20H20N4O6[α]D26=+418.4 (c 0.4, CHCl3)Source of chirality: (S,S)-1,2-cyclohaxanediamineAbsolute configuration: (1S,2S)(1S,2S,NZ,N′Z)-N,N′-Bis(4-methoxybenzylidine)cyclohexane-1,2-diamine N,N′-dioxideC22H26N2O4[α]D22=+185.8 (c 0.34, CHCl3)Source of chirality: (S,S)-1,2-cyclohaxanediamineAbsolute configuration: (1S,2S)(1S,2S,NZ,N′Z)-N,N′-Bis(3,4,5-trimethoxybenzylidene)cyclohexane-1,2-diamine N,N′-dioxideC26H34N2O8[α]D22=+111.9 (c 1.0, CHCl3)Source of chirality: (S,S)-1,2-cyclohaxanediamineAbsolute configuration: (1S,2S)(R)-1-(3,4,5-Trimethoxyphenyl)but-3-en-1-olC13H18O4Ee = 87%[α]D31=+32.2 (c 2.9, CHCl3)Source of chirality: enantioselective synthesisAbsolute configuration: (R)

N-Acylated β-amino enones reductively cyclize by treatment with trichlorosilane and a chiral Lewis base catalyst to afford optically active 4H-1,3-oxazines, which can be transformed to other chiral compounds without racemization.

Lewis bases such as Ph3PO and HMPA catalyze the 1,4-reduction of α,β-unsaturated ketones with trichlorosilane, and because the 1,2-reduction of aldehydes scarcely proceeded under the conditions, one-pot reductive aldol reactions with aldehydes were successfully achieved; preliminary studies using a chiral Lewis base revealed a high potential for enantioselective catalysis.

Treatment of an optically pure tartaric acid-derived diiodide and various secondary phosphine oxides with LHMDS provides the corresponding aryl group-modified DIOP dioxides (Ar-DIOPOs). The activities of Ar-DIOPOs as Lewis base catalysts were investigated for several asymmetric transformations using chlorosilane reagents. The p-tolyl-substituted DIOPO (p-tolyl-DIOPO) was most effective for the reductive aldol reaction of chalcone and aldehydes with trichlorosilane, whereas the 2,8-dimethylphenoxaphosphine-derived DIOPO (DMPP-DIOPO) afforded the best enantioselectivity for the phosphonylation of conjugated aldehydes and the chlorinative aldol reaction of an ynone and benzaldehyde.

N-Acylated β-amino enones reductively cyclize by treatment with trichlorosilane and a chiral Lewis base catalyst to afford optically active 4H-1,3-oxazines, which can be transformed to other chiral compounds without racemization.

We have found that O-monoacyltartaric acids catalyze asymmetric conjugate addition of boronic acids to enones with good enantioselectivity, and the 3,5-di(tert-butyl)benzoyl group provides the best results among the acyl groups examined.

Lewis bases such as Ph3PO and HMPA catalyze the 1,4-reduction of α,β-unsaturated ketones with trichlorosilane, and because the 1,2-reduction of aldehydes scarcely proceeded under the conditions, one-pot reductive aldol reactions with aldehydes were successfully achieved; preliminary studies using a chiral Lewis base revealed a high potential for enantioselective catalysis.