Herein, an unprecedented switching of circularly polarized luminescence (CPL) is described for chiral 4,6-bis(1-(pyren-1-ylamino)propyl)dibenzo[b,d]furan (1). The CPL band of chiral diamine 1, which contains two pyrene rings, can be switched between the monomer and excimer emission regions under concomitant inversion of the handedness, simply by changing the concentration of the fluorophore. In contrast, the maximum photoluminescence (PL) intensity is always observed in the monomer region, regardless of the concentration. The reversal of the intensity ratio of monomer and excimer emission between PL and CPL was attributed to a stronger CPL (|gem| = ∼3–4 × 10−3) contribution from the minor excimer component, which should exhibit an efficient chiral environment around the dimeric pyrenes.

A series of o-xylylene-type chiral 1,4-amino alcohols with an aminal structure was synthesized starting from (S)-2-(arylaminomethyl)pyrrolidine, o-bromobenzaldehyde, and a diaryl ketone. The enantioselective addition of diethylzinc to aldehydes was examined by using the 1,4-amino alcohols, and the corresponding chiral secondary alcohols were obtained with high enantioselectivities (up to 98% ee).(3R,7aS)-3-(2-Bromophenyl)-2-phenylhexahydro-1H-pyrrolo[1,2-c]imidazoleC18H19BrN2[α]D23=+124 (c 1.0, CH2Cl2)Source of chirality: l-prolineAbsolute configuration: (3R,7aS)(3R,7aS)-3-(2-Bromophenyl)-2-(4-methoxyphenyl)hexahydro-1H-pyrrolo[1,2-c]imidazoleC19H21BrN2O[α]D19=+96.2 (c 1.0, CHCl3)Source of chirality: l-prolineAbsolute configuration: (3R,7aS)(3R,7aS)-3-(2-Bromophenyl)-2-(4-(trifluoromethyl)phenyl)hexahydro-1H-pyrrolo[1,2-c]imidazoleC19H18BrF3N2[α]D19=+86.7 (c 1.0, CHCl3)Source of chirality: l-prolineAbsolute configuration: (3R,7aS)Diphenyl(2-((3R,7aS)-2-phenylhexahydro-1H-pyrrolo[1,2-c]imidazol-3-yl)phenyl)methanolC31H30N2O[α]D28=+292.9 (c 1.0, CHCl3)Source of chirality: l-prolineAbsolute configuration: (3R,7aS)(2-((3R,7aS)-2-(4-Methoxyphenyl)hexahydro-1H-pyrrolo[1,2-c]imidazol-3-yl)phenyl)diphenylmethanolC32H32N2O2[α]D23=+210.4 (c 1.1, CHCl3)Source of chirality: l-prolineAbsolute configuration: (3R,7aS)Diphenyl(2-((3R,7aS)-2-(4-(trifluoromethyl)phenyl)hexahydro-1H-pyrrolo[1,2-c]imidazol-3-yl)phenyl)methanolC32H29F3N2O[α]D23=+227.0 (c 1.3, CHCl3)Source of chirality: l-prolineAbsolute configuration: (3R,7aS)(2-((3R,7aS)-2-Phenylhexahydro-1H-pyrrolo[1,2-c]imidazol-3-yl)phenyl)di-p-tolylmethanolC33H34N2O[α]D28=+281.0 (c 1.0, CHCl3)Source of chirality: l-prolineAbsolute configuration: (3R,7aS)Bis(4-methoxyphenyl)(2-((3R,7aS)-2-phenylhexahydro-1H-pyrrolo[1,2-c]imidazol-3-yl)phenyl)methanolC33H34N2O3[α]D23=+281.7 (c 1.0, CHCl3)Source of chirality: l-prolineAbsolute configuration: (3R,7aS)(2-((3R,7aS)-2-Phenylhexahydro-1H-pyrrolo[1,2-c]imidazol-3-yl)phenyl)bis(4-(trifluoromethyl)phenyl)methanolC33H28F6N2O[α]D28=+241.6 (c 1.0, CHCl3)Source of chirality: l-prolineAbsolute configuration: (3R,7aS)(2-((3R,7aS)-2-Phenylhexahydro-1H-pyrrolo[1,2-c]imidazol-3-yl)phenyl)bis(3-(trifluoromethyl)phenyl)methanolC33H28F6N2O[α]D28=+253.3 (c 1.0, CHCl3)Source of chirality: l-prolineAbsolute configuration: (3R,7aS)(2-((3R,7aS)-2-Phenylhexahydro-1H-pyrrolo[1,2-c]imidazol-3-yl)phenyl)bis(2-(trifluoromethyl)phenyl)methanolC33H28F6N2O[α]D28=+199.8 (c 1.0, CHCl3)Source of chirality: l-prolineAbsolute configuration: (3R,7aS)Bis(3,5-bis(trifluoromethyl)phenyl)(2-((3R,7aS)-2-phenylhexahydro-1H-pyrrolo[1,2-c]imidazol-3-yl)phenyl)methanolC35H26F12N2O[α]D28=+205.0 (c 0.47, CHCl3)Source of chirality: l-prolineAbsolute configuration: (3R,7aS)(2-((3R,7aS)-2-Phenylhexahydro-1H-pyrrolo[1,2-c]imidazol-3-yl)phenyl)bis(3,4,5-trifluorophenyl)methanolC31H24F6N2O[α]D21=+215.0 (c 1.0, CHCl3)Source of chirality: l-prolineAbsolute configuration: (3R,7aS)Bis(perfluorophenyl)(2-((3R,7aS)-2-phenylhexahydro-1H-pyrrolo[1,2-c]imidazol-3-yl)phenyl)methanolC31H20F10N2O[α]D23=+144.0 (c 0.94, CHCl3)Source of chirality: l-prolineAbsolute configuration: (3R,7aS)

A series of o-xylylene-type 1,4-amino alcohols, synthesized from (R)-1-phenylethylamine, were used as chiral ligands for the enantioselective addition of diethylzinc to benzaldehyde. (S)-1-Phenyl-1-propanol was obtained with high enantioselectivity in all cases since the stereochemical outcome of the reaction was controlled by the chiral benzylic carbon bearing amino group. Highest catalytic activity was obtained by using (R)-1-{2-[1-(pyrrolidin-1-yl)ethyl]phenyl}cyclohexan-1-ol (1n) derived from (R)-1-(1-phenylethyl)pyrrolidine and cyclohexanone. Various chiral secondary alcohols were obtained by the reaction of diethylzinc and aldehydes in the presence of 1n within 2 h with good to high enantioselectivities.

Mesoporous aluminosilicate (Al-MCM-41) was found to be an effective and reusable catalyst for 1,3-addition of silyl enol ethers to nitrones. The reaction proceeded under mild reaction conditions to afford the corresponding β-(siloxyamino)ketones in high yields. Furthermore, a unique chemoselectivity of a nitrone over an aldehyde and an acetal, which are more reactive toward silyl enol ether in the presence of Al-MCM-41 than a nitrone, was observed.

In the presence of a catalytic amount of mesoporous aluminosilicate (Al-MCM-41), both allyltrimethylsilane and silyl enol ether reacted with various acetals under mild reaction conditions to afford the corresponding homoallyl ethers and β-alkoxy ketones, respectively. The catalyst was easily recovered from the reaction mixture and could be reused in the same reaction without a significant loss of catalytic activity. Moreover, Al-MCM-41 exhibited high chemoselectivity for acetal over aldehyde in the reactions.

The catalytic asymmetric borane reduction of prochiral ketones was examined in the presence of chiral diazaborolidine catalysts prepared in situ from chiral β-diamines and borane. Chiral secondary alcohols were obtained with modest to high enantiomeric excesses (up to 92% ee) using (S)-2-[(4-trifluoromethyl)anilinomethyl]indoline 2f.

Herein, an unprecedented switching of circularly polarized luminescence (CPL) is described for chiral 4,6-bis(1-(pyren-1-ylamino)propyl)dibenzo[b,d]furan (1). The CPL band of chiral diamine 1, which contains two pyrene rings, can be switched between the monomer and excimer emission regions under concomitant inversion of the handedness, simply by changing the concentration of the fluorophore. In contrast, the maximum photoluminescence (PL) intensity is always observed in the monomer region, regardless of the concentration. The reversal of the intensity ratio of monomer and excimer emission between PL and CPL was attributed to a stronger CPL (|gem| = ∼3–4 × 10−3) contribution from the minor excimer component, which should exhibit an efficient chiral environment around the dimeric pyrenes.