2163-12-4

The Fries rearrangement of 3-chlorophenyl acetate provided the expected 4-chloro-2-hydroxy-acetophenone as the major product and 2,4-diacetyl resorcinol and 2-chloro-4-hydroxy-acetophenone as minor products. 4-Benzyloxy-2-chloroacetophenone was prepared by a Heck reaction and then elaborated to 4-benzyloxy-2-chlorophenacyl azide.

Chalcones have a distinctive 1,3-diarylpropenone skeleton and exert numerous biological effects. Using a one-step Claisen-Schmidt condensation, we synthesized eleven bis-chalcones (3-13) and three acetyl chalcones (14-16) from substituted aldehydes and diacetylresorcinol. The compounds were tested for in vitro cytotoxic activity against four human cancer cell lines (A549, DU145, KB, and KB-VIN) and inhibition of NO production in lipopolysaccharide (LPS)-activated microglial cells. Among them, four compounds (3, 5, 6, and 13) showed significant cytotoxic activity with EC50 values ranging from 1.57 to 5.14 μM, and seven compounds (3, 5-8, 10, and 13) displayed potent anti-inflammatory activity by inhibiting NO production with IC50 values ranging from 0.95 to 8.65 μM. A mechanism of action study of active compounds 6 and 7 discovered that these compounds down-regulated iNOS expression by inhibiting p65 NF-κB activation/nuclear translocation due to prevention of IκBα degradation. Structure-activity relationship (SAR) findings are also discussed.

Zinc powder in the presence of N,N-dimethylformamide efficiently catalyzes the selective Fries rearrangement of acetylated phenols under microwave heating or with conventional heating using an oil bath. In some cases different products were obtained using microwave heating and conventional heating. Selective migration of the acyl group has been noted with good yields.

1,3-Dibenzoyl-2,4-diacyl- and 1,5-Dibenzoyl-2,4-diacylbenzene are prepared in good yields via a further application of a recently reported two step replacement of phenolic hydroxyl by an acyl group.

Claisen rearrangements of the 3-methylbut-2-enyl(prenyl)ethers 3 and 9 of 2-acetyl-1-hydroxy- and 1-acetyl-2-hydroxynaphthalenes 1 and 2 and the bis(3-methylbut-2-enyl)ethers 12 and 18 of 2,4- and 4,6-diacetylresorcinols 11 and 17 have been studied under a variety of thermal and catalytic conditions. 2-Acetyl-4-(3-methylbut-2-enyl)naphthalene-1-ol 4 was the sole product on rearrangement of compound 3, in DMA or neat.Under catalytic conditions 3,4-dihydro-2,2-dimethyl-2H-naphthopyran 7 was obtained in poor yield.An isomeric pyran, 1,2-dihydro-3,3-dimethyl-3H-naphthopyran 10 (25-43percent) was obtained under both thermal and catalytic conditions from 9.The rearrangement of 12 under thermal conditions (DMA and neat) furnished 3-acetyl-2,4-dihydroxy-5-(3-methylbut-2-enyl)acetophenone 13 and 3,8-diisopropylbenzodifuran 14.Pd'' mediated rearrangement of 12 gave only the partially deprenylated ether, 3-acetyl-4-hydroxy-2-(3-methylbut-2-enyloxy)acetophenone 15 (29percent).While the isomeric ether 18 gave the monoprenyl ether, 5-acetyl-4-hydroxy-2-(3-methylbut-2-enyloxy)acetophenone 19 in quantitative yield (95percent).The rearrangment products were characterised and their formation rationalised in terms of allowed sigmatropic shifts( prenyl and H) followed by loss of prenyl or acetyl groups.The reactions of prenyl ethers are both comparable to those of the corresponding allyl ethers and consistent with the greater fixed double-bond character of the naphthalene system compared to that of benzene.Prenyl derivatives of benzene and naphthalene containing ortho - hydroxyacetophenone units were formed which have potential in synthesis.

Acetic anhydride/zinc chloride has been found to be a better acylating system for phenol and polyphenols resulting in improved yields of the respective hydroxyacetophenones.The phenols used are phenol, resorcinol, hydroquinonone, catechol, phloroglucinol and pyrogallol.With resorcinol the isomeric diacetyl derivatives are formed in excellent yields in a single step, while catechol and hydroquinone give only monoacetyl derivatives like simple phenol.Pyrogallol gives a monoacetyl derivative while phloroglucinol gives both mono and diacetyl derivatives but not triacetyl derivatives.