Studies in sesquiterpenes—XLIII

Pore-engineered silica–alumina: texture, acidity, and activity for conversion of longifolene to isolongifolene

“…Several investigations were reported on the conversion of longifolene to isolongifolene using acids like sulfuric acid/acetic acid [15], BF 3 ÁOEt 2 [16,17], bromoacetic acid [18], camphenecarboxylic acid [19], and others [20,21]. The disadvantages inherent in the use of acids are multiple steps, long reaction times, and above all the existing processes are not eco-friendly [15].…”

Influence of acidity of montmorillonite and modified montmorillonite clay minerals for the conversion of longifolene to isolongifolene

“…Isolongifolene a tricycle sesquiterpene is produced by deep-seated rearrangement of longifolene involving a number of steps catalyzed by acids like sulfuric acid, acetic acid, BF 3 , amberlyst-15 or acid treated silica gel [7][8][9][10]. In view of the industrial importance of this compound, patents have closely guarded the details of the catalysts and process parameters.…”

Synthesis of morphine analogues. Part 1. Synthesis of some 5-benzyl-2-methyloctahydroisoquinolines

“…In the initial methylation the required compound (4) and its methyl ester were formed in the proportions 20 : 80, but alkaline hydrolysis of this mixture followed by workup gave a 95' ;: overall yield of (4) in a ' one-pot ' reaction. The conversion of the arylpropanoic acid into its acid cliloritle and catalytic reduction with 5% palladium-barium sulphate (Rosenmund reduct ion 3, gave 3-(2-methoxyphenyl)propanal (5) in 85% yield. An alternative reduction of the acid chloride with tri-tbutoxyaluminium hydride was unsatisfactory, giving 8% of the aldehyde (5) and 40% of the corresponding alcohol.…”

“…The conversion of the arylpropanoic acid into its acid cliloritle and catalytic reduction with 5% palladium-barium sulphate (Rosenmund reduct ion 3, gave 3-(2-methoxyphenyl)propanal (5) in 85% yield. An alternative reduction of the acid chloride with tri-tbutoxyaluminium hydride was unsatisfactory, giving 8% of the aldehyde (5) and 40% of the corresponding alcohol.…”

“…The allylic alcohol (6) was obtained from a Grignard reaction of the aldehyde (5) with vinylmagnesium bromide; the yield varied between 50 and 67%, the remainder of the aldehyde being accounted for as the trimer (13). Oxidation of the allylic alcohol with Jones reagent resulted in quantitative conversion of (6) into (7) with an overall yield of (7), based on the starting dihydrocoumarin, of greater than 40 yo.…”