GB828591A - Novel bicyclic compounds and a process for the manufacture thereof - Google Patents

Abstract

The invention comprises 1-hydroxy-naphthalenes of the formul <FORM:0828591/IV (b)/1> <FORM:0828591/IV (b)/2> and esters thereof and 1-keto-naphthalenes of the formul <FORM:0828591/IV (b)/3> <FORM:0828591/IV (b)/4> <FORM:0828591/IV (b)/5> where R1, R2 and R3 represent optional alkyl groups containing up to six carbon atoms (the broken lines denoting the optional bonds thereto). The preferred compounds are those in which R1, R2 and R3 are absent, i.e. the 2,5,5,9 - tetramethyl substituted compounds. The compounds may be prepared by a process which comprises or includes as a first step treating an aldehyde of the formula <FORM:0828591/IV (b)/6> with an acidic agent to give the unsaturated alcohol I. The alcohol I may then be treated by methods known per se for the purposes of esterification, isomerization, hydrogenation of the double bond or oxidation of the hydroxyl group and one or more such operations may be carried out in any order. The cyclization of the aldehyde preferably takes place in the presence of phosphoric acid and in the absence of any solvents, the acidic agent may, however, be formic or acetic acid in which case the appropriate ester of alcohol I is directly obtained. Esterification of the alcohols may be carried out using acid halides or anhydrides in the presence of pyridine, hydrogenation of the double bond catalytically in the presence of palladium, oxidation of the hydroxy group with chromic acid in acetic acid, isomerization at the double bond of the unsaturated ketone by means of sulphuric acid and isomerization of the alcohol at the hydroxy group by oxidizing it to a keto group and then reducing the ketone with lithium aluminium hydride. In the examples: (1) 4 - [21,61,61 - trimethyl - cyclo - hexen - 11 - yl] - 2 - methyl - butanal - 1 is cyclized to give 2,5,5,9 - tetramethyl - 1 - hydroxy - 1,2,3,5,6,7,8,9-octahydronaphthalene and its esters are prepared with formic, acetic and benzoic acids; the unsaturated alcohol is reduced to the corresponding saturated alcohol (type II) which is in turn oxidized to the saturated ketone (type V), hydride reduction of this ketone gives a saturated alcohol isomeric with the one mentioned above; the unsaturated alcohol (type I) is oxidized to the ketone (type III) which is isomerized to ketone (type IV) and then reduced to a saturated ketone (type V) which is isomeric with the one mentioned above; (2) and (3) the formate and acetate esters of the unsaturated alcohol (type I) above are directly prepared by cyclizing the aldehyde in the presence of formic and acetic acids.