Patent GB-713767-A (GB)
Title: Improvements relating to substituted quinazolones
IPC: C07D401/06
Filed: 1951-09-05
Abstract: The invention comprises quinazolones of the general formula <FORM:0713767/IV (b)/1> wherein R represents at least one of the following: halogen atoms, alkoxy, aryloxy, aralkoxy hydroxy, aryl, alkyl, acyl and carboxyl radicals in one or more of the 5, 6, 7 and 8 positions; R1 represents a hydrogen atom or a hydroxy, alkoxy or aryloxy radical.  The compounds may be prepared by subjecting quinazolones of the general formula <FORM:0713767/IV (b)/2> (wherein R11 represents -OC2H5; -O.CH2. C6H5; -O.C6H5; C6H5 or substituted phenyl radicals) to acid hydrolysis until the group -COR11 has been replaced by a hydrogen atom, and, where R1 is an alkoxy group, optionally further subjecting the resulting product to dealkylation. The acid hydrolysis is carried out using a strong inorganic acid, e.g. hydrohalic, sulphuric and phosphoric acids.  In numerous detailed examples quinazolones of general formula II are refluxed in hydrochloric acid, evaporated to dryness and the products purified from ethanolic hydrogen chloride.  For the preparation of compounds in which R1 is hydroxy, the corresponding methoxy derivative is refluxed in hydrobromic acid, evaporated to dryness and purified as above.  The preparation is described of formula I compounds in which R1 is -OH or -OCH3 and R is 5-Cl; 6-Cl; 7-Cl; 8-Cl; 5-F; 5-CF3; 5-Br; 5-Me; 6-Me; 7-Me; 8-Me; 5-OMe; 6-OMe; 5-Cl, 8-MeO; 5-Cl, 6-Me; 6 : 8-di-Cl; or 5 : 6-di-Me.  Quinazolones of general formula II are prepared by condensation of a 4-quinazolone of the general formula <FORM:0713767/IV (b)/3> with a substituted piperidine having the general formula <FORM:0713767/IV (b)/4> wherein X represents a halogen atom.  In an example 6-chloro-4-quinazolone in sodium methoxide is treated with 1-carbethoxy-2-(g -bromoacetonyl)-3-methoxypiperidine to produce 3-[b  - keto - g  - (1 - carbethoxy - 3 - methoxy - 2-piperidyl) - propyl] - 6 - chloro - 4 - quinazolone.  Other formula II quinazolones in which R and R1 represent the radicals listed above and R11 is a carbethoxy group are also described.  The requisite 4-quinazolones are prepared from the corresponding anthranilic acids by fusion with formamide, a number of the necessary anthranilic acids being obtained from suitable isonitroso acetanilides by cyclization to the isatins followed by treatment with alkaline hydrogen peroxide.  Detailed preparations of 8-chlor, 5-chloro - 8 - methoxy -, 5 - chloro -, 6 : 8 - dichloro-, 5 - bromo -, 5 - chloro - 6 - methyl -, 5 : 6 - dimethyl -, and 5 - trifluoromethyl - 4 - quinazolones are given.  5-Methoxy- and 5-fluoro-4-quinazolone are obtained by cyclization of 2-formylamino-6-methoxybenzamide and by diazotization of 5-amino-4-quinazolone respectively.  The necessary substituted piperidines are prepared from 2-piperidones. In a detailed example, 3-chloro-3-carbethoxy-2-piperidone is converted to 3-methoxy-3-carbomethoxy-2-piperidone which upon treatment with acid and then benzyl chlorocarbonate yields 2-methoxy-5-carbobenzoxyaminovaleric acid.  Conversion to the acid chloride followed by condensation with ethyl malonate furnishes ethyl (2-methoxy-5-carbobenzoxyamino valeryl) malonate which is hydrogenated to 3-methoxy piperidine-2-malonic ester, which upon hydrolysis and reaction with ethyl chlorocarbonate yields 1-carbethoxy-3-methoxy-2-piperidylacetic acid.  This is converted via its acid chloride, treatment with diazomethane and finally hydrobromic acid into 1 - carbethoxy - 2 - [g  - bromoacetonyl] - 3 - methoxypiperidine.