Patent FR-2775284-A1 (FR)
Title: Preparation of aromatic ketones by reaction of a dihalo aromatic compound with an alpha ketone - using hydrogen, a base and a Group VIII metal complex
Inventor: DESMURS JEAN ROGER
IPC: C07B37/04
Filed: 1998-02-20
Abstract: An aromatic ketone is prepared from an aromatic compound having two halogen atoms and an electron donor group ortho to these halogen atoms, by reacting this compound with an  alpha -keto olefin in the presence of hydrogen, a base, and a catalyst that is a Group VIII element complexed with a coordination agent or ligand. The halo-aromatic compound used as starting material is preferably of formula (I) A = the residue of a ring forming part of a carbocyclic or heterocyclic, aromatic, mono- or polycyclic system; R = an electro-donor group; X = halogen; n = one or more; m = two or more A is preferably composed of at least 4 atoms (preferably 5 or 6, optionally substituted), or is the residue of a benzene or naphthalene ring; R is preferably H, OH, 1-6C linear or branched alkyl (especially 1-4C), phenyl, OR1, NR2R3, NHCOR2, F (especially H, OH, 1-4C alkyl, methoxy methylene dioxy or ethylene dioxy). R1 = 1-6C linear or branched alkyl (preferably 1-4C) or phenyl; R2, R3 = H, 1-6C linear or branched alkyl (1-4C) or phenyl; When n is greater than or equal to 2, 2 R groups and 2 successive atoms of the aromatic ring can be linked together by a 2-4C alkyl, alkenyl or alkenylidene group forming a heterocycle of 5-7C. 1 or more C may be replaced by a heteroatom, preferably oxygen. Especially preferred, is the case where (I) is 1,6-dibromo-2-methoxy naphthalene. The  alpha -keto olefin is of formula (II)  R0 = H, benzyloxycarbonyl or alkyloxycarbonyl Preferably, (II) is methyl vinyl ketone or 3-(benzyloxy carbonyl)-but-3-en-2-one, 1.2 - 1.5 moles preferably being used per mole of the halo aromatic compound.   The catalyst is a finely divided Group VIII metal (palladium, rhodium or iridium) or a mineral or organic acid salt of them, preferably Pd II acetate, propionate, butyrate or benzoate, or palladous chloride, coordinated to an aliphatic, cycloaliphatic, arylaliphatic or mixed phosphine PR5R6R7 (III). The catalyst is in a molar ratio compared to (I) or (I') of 10<-5> to 10<-1>, preferably 10<-4> to 10<-2>.   R5, R6, R7 = 1-12C alkyl, 5-6C cycloalkyl (optionally substituted by 1 or more 1-4C alkyl or akoxy), phenyl-1-6C-alkyl; or 1 or 2 of R5,R6, and R7 are phenyl, optionally substituted by 1 or more 1-4C alkyl or alkyloxy The present invention is particularly applicable to the synthesis of haloaromatics of the fused structure (I') p = 0,1 n', m' = 0-2 The base is preferably a tertiary amine N(R8)3, present in sufficient quantity to neutralize the acid liberated by the reaction. R8 = independently 1-20C alkyl, cycloalkyl, aryl or heterocyclic, or 2 R8 together with the N form a heterocycle of 4-6 atoms (preferably 1-10C alkyl (especially 1-4C) or cyclopentyl, cyclohexyl or pyridinyl) The reaction is preferably carried out at 50 - 250  deg C, especially 100 - 200  deg C and at a pressure of 1 - 100 bar, especially 10 - 50 bar.  An Independent claim is also provided for the use of 1-(2'-methoxynaphth-6'-yl)but-2-en-3-one, obtained by this process, as an intermediate for the preparation of 1-(2'-methoxynaphth-6-yl)butan-3-one.