Reagents for Bromination; Application in the Synthesis of Diterpenes, Sesquiterpenes and Bioactive Compounds

Abstract

Several organic compounds especially cyclic compounds containing double or triple bond and carbonyl compounds, aromatic compounds were brominated by employing several well-known reagents e.g., Nbromosuccinimide, bromine in acetic acid, ammonium bromide, hydrogen peroxide in acetic acid, carbon tetrabromide, phosphorous tribromide, 2,4,4,6-tetrabromocyclohex-2,5-dienone. The resulting compounds were utilized for the synthesis of several sesquiterpenes e.g., eudes-4(14)7(11)-diene-8-one, glutinosone, platyphyllide, occidentalol, drim-8-ene-7-one, cacalol, elemol, bakkenolide A, 10-bromo-α-chamigrene, allolaurintero, aplysin, costunolide, humulene, bisabollenes, bicycloelemene, occidol, longifolin, juvabiols, futronolide, etc. The importance of some of the mentioned reagents for bromination was also observed during the synthesis of the plant hormone abscisic acid, marine terpene synderol and α-asarone, a substance of potent hypolipidemic activity. The compounds obtained by bromination were likewise utilized for the synthesis of diterpenes like taxodione, spat-13,17- dien-5-ol and gibberellin A12. Some of these bromo compounds were utilized for the synthesis of many substituted tetralones, tetralins and naphthalenes e.g., 6,7-dimethoxy-2-tetralone, 8-methyl-7-methoxy-1-tetralone, 8- methyl-1-tetralone, 1,4-dimethoxy-1-acetylnaphthalene, 7-methoxy-1-naphthylacetic acid, 5,6-dimethoxy- 1,2,3,4-tetrahydronaphthalene-2-carboxylic acid, 2-hydroxy-1,4-dimethoxynaphthalene which were utilized for the synthesis of many bioactive compounds. Dedicated with profound regards to Dr. Michael Kolb, ex-editor of Synthetic Communications Keywords: N-bromosuccinimide (NBS), bromine in acetic acid, carbon tetrabromide, ammoniun bromide, hydrogen peroxide, phosphorous tribromide, silver tetrafluoroborate, bromine.