Catalytic asymmetric hydrosilylation of acetophenone with new chiral thiourea ligands containing the (S)-α-phenylethyl group

New chiral thioureas 1–8 containing 1,2-ethylendiamine or trans-1,2-diaminocyclohexane as the carbon skeleton, and containing an (S)-α-phenylethyl group have been prepared (79–98% yield). Thioureas 1–8 were used as ligands for the zinc-based catalyzed asymmetric hydrosilylation of acetophenone with polymethylhydrosiloxane (PMHS). The best result was achieved with monothiourea 1 (up to 75% ee), in toluene and a catalyst load of 5 mol %.

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(1S,2S)-N,N′,N′′-Tris[(S)-α-phenylethyl]-1,2-diaminocyclohexylthioureaC31H39N3S[α]D=+18[α]D=+18 (c 1, CHCl3)Source of chirality: (S)-α-phenylethylamineAbsolute configuration: (1S,2S,1′S,1′′S,1′′′S)

(1S,2S)-N,N′-Bis[(S)-α-phenylethyl]-N′′-(1-naphthylethyl)-1,2-diaminocyclohexylthioureaC35H41N3S[α]D=+12[α]D=+12 (c 1, CHCl3)Source of chirality: (S)-α-phenylethylamineAbsolute configuration: (1S,2S,1′S,1′′S,1′′′S)

(1S,2S)-N,N′-Bis[(S)-α-phenylethyl]-N′′-(benzyl)-1,2-diaminocyclohexylthioureaC30H37N3S[α]D=+13[α]D=+13 (c 1, CHCl3)Source of chirality: (S)-α-phenylethylamineAbsolute configuration:(1S,2S,1′S,1′′S)

(1S,2S)-N,N′-Bis[(S)-α-phenylethyl]-N′′-[di(phenyl)methylene]-1,2-diaminocyclohexylthioureaC36H41N3S[α]D=+19[α]D=+19 (c 1, CHCl3)Source of chirality: (S)-α-phenylethylamineAbsolute configuration: (1S,2S,1′S,1S′′)

N,N′-Bis[(S)-α-phenylethyl]-1,2-diaminoethylendithioureaC20H26N4S2[α]D=+37[α]D=+37 (c 1, CHCl3)Source of chirality: (S)-α-phenylethylamineAbsolute configuration: (1′S,1′′S)

N,N′,N′′,N′′′-Tetraquis[(S)-α-phenylethyl]-1,2-diaminoethylendithioureaC36H42N4S2[α]D=-0.7[α]D=-0.7 (c 1, CHCl3)Source of chirality: (S)-α-phenylethylamineAbsolute configuration: (1′S,1′′S,1′′′S,1′′′′S)

N,N′-Bis[(S)-α-phenylethyl]-N′′,N′′′-bis(benzyl)-1,2-diaminoethylendithioureaC34H38N4S2[α]D=-68[α]D=-68 (c 1, CHCl3)Source of chirality: (S)-α-phenylethylamineAbsolute configuration: (1′S,1′′S)

N,N′-Bis[(S)-α-phenylethyl]-N′′,N′′′-bis(phenyl)-1,2-ethylendithioureaC32H34N4S2[α]D=-120[α]D=-120 (c 1, CHCl3)Source of chirality: (S)-α-phenylethylamineAbsolute configuration: (1′S,1′′S)