Preparation and x-ray crystal structure of (2Z,4E)-5-(4-substituted phenyl)-3-hydroxy-1-phenylpenta-2,4-dien-1-ones (Curcumin Analogs) from the condensation-elimination of dilithiated 1-benzoylacetone with substituted benzaldehydes

摘要

1-Benzoylacetone 1 was dilithiated with lithium diisopropylamide or lithium hexamethyl-disilazide, and the resulting dianion type intermediate 1a was condensed with (lithium) 4-hydroxybenzaldehyde, 4-dimethylaminobenzaldehyde, or 4-chlorobenzaldehyde to afford hydroxyl-β-diketones that were not isolated but underwent linear dehydration to afford products, (2Z,4E)-5-(4-hydroxyphenyl) -3-hydroxy-1-phenylpenta-2,4-dien-1-one 2 C_(17)H_(14)O _3; (2Z,4E)-5-(4-(dimethylamino)phenyl)-3-hydroxy-1-phenylpenta-2,4- dien-1-one 3 C_(19)H_(19)NO_2; and (2Z,4E)-5-(4-chlorophenyl)-3-hydroxy-1-phenylpenta-2,4-dien-1-one 4 C _(17)H_(13)ClO_2. Crystals of C_(17)H _(14)O_3 2 are orthorhombic, Pna2_1, a = 20.937(4) ?, b = 11.683(3) ?, c = 5.490(1) ?, Z = 4, V = 1343.1(5) ?~3, R _1 = 0.0478 and wR _2 = 0.1143 for reflections with I > 2σ(I); crystals of C_(19)H _(19)NO_2 3 are monoclinic, P2_1/c, a = 16.637(3) ?, b = 10.736(2) ?, c = 9.197(1) ?, β = 105.670(5), Z = 4, V = 1581.7(5) ?~3, R 1 = 0.0609 and wR 2 = 0.1491 for reflections with I > 2σ(I); crystals of C~(17)H~(13) ClO_2 4 are monoclinic, P2_1/c, a = 31.574(6) ?, b = 5.780(1) ?, c = 7.423(2) ?, β = 94.47(3), Z = 4, V = 1350.5(5) ?3, R _1 = 0.0696 and wR _2 = 0.2423 for reflections with I > 2σ(I). Graphical Abstract: X-ray crystal analysis was essential for identifying which tautomer resulted from the condensation-elimination of dilithiated 1-benzoylacetone with select substituted benzaldehydes to form curcumin analogs, (2Z,4E)-5-(4- substituted phenyl)-3-hydroxy-1-phenylpenta-2,4-dien-1-ones. Each crystalline compound showed the same curcumin-enol bonding structural features. [Figure not available: see fulltext.]