An enantioselective and regioselective total synthesis approach to chiral 1,4-benzodioxane lignans(2R,3R)- and (2S,3S)-2-(4-hydroxy-3-methoxyphenyl)-3-hydroxymethyl-1,4-benzodioxan-6-carbaldehyde was reported firstly.
Four new chiral aminodiols 1-4, which were prepared from methyl L proline in 2 steps, were applied in the enantioselective addition of diethylzinc to benzaldehyde. The results indicated that the enantioselectivities e...Four new chiral aminodiols 1-4, which were prepared from methyl L proline in 2 steps, were applied in the enantioselective addition of diethylzinc to benzaldehyde. The results indicated that the enantioselectivities enhance with increasing the bulkiness of substituents on chiral ligands and with chiral ligand 4 giving the best result. When ligand 4 was used to catalyze the enantioselective addition of diethylzinc to aromatic aldehydes, the substituents affect the enantioselectivities slightly and 1 naphthaldehyde gives the best enantiomeric excess(up to 75.3% ). On the other hand, 4 (dimethylamino)benzaldehyde gives a low enantiomeric excess, which may most likely arise from a non steroselective ethyl transfer to aldehyde promoted by zinc coordination of amino group. For aliphatic aldehydes, poor enantiomeric excesses are generally given.展开更多
文摘An enantioselective and regioselective total synthesis approach to chiral 1,4-benzodioxane lignans(2R,3R)- and (2S,3S)-2-(4-hydroxy-3-methoxyphenyl)-3-hydroxymethyl-1,4-benzodioxan-6-carbaldehyde was reported firstly.
文摘Four new chiral aminodiols 1-4, which were prepared from methyl L proline in 2 steps, were applied in the enantioselective addition of diethylzinc to benzaldehyde. The results indicated that the enantioselectivities enhance with increasing the bulkiness of substituents on chiral ligands and with chiral ligand 4 giving the best result. When ligand 4 was used to catalyze the enantioselective addition of diethylzinc to aromatic aldehydes, the substituents affect the enantioselectivities slightly and 1 naphthaldehyde gives the best enantiomeric excess(up to 75.3% ). On the other hand, 4 (dimethylamino)benzaldehyde gives a low enantiomeric excess, which may most likely arise from a non steroselective ethyl transfer to aldehyde promoted by zinc coordination of amino group. For aliphatic aldehydes, poor enantiomeric excesses are generally given.
