Synthesis of heterocyclic three-fused ring compounds using molecular sieve catalysts

Abstract

Abstract The reaction of cyclohexanone, formaldehyde and ammonia was carried out over zeolite/molecular sieve catalysts. The major products obtained were octahydrophenanthridine, octahydroacridine, cyclohexanoneoxime, cyclohexamine. The reaction of cyclohexanone, formaldehyde and ammonia was carried out over molecular sieve catalysts in an autoclave under 4-49 atm autogeneous pressure. The molar ratio of cyclohexanone:formaldehyde:NH 3 was 1:1:3 and 222 ml of methanol was used as a solvent. The selectivities for octahydrophenanthridine were 32.2, 44.4, 60.6 and 50.2 percent at 98.7, 97.7, 83.0 and 53.0 percent conversions of cyclohexanone at 215, 170, 150 and 100°C respectively. The catalyst used was H-beta. The selectivities for octahydroacridine were 42.2, 39.4, 21.7 and 7.7 percent respectively. The effect of molar ratio, various solvents, various catalysts and reactants have been studied. The best catalysts observed were (Hp)H-beta and HMCM-41. The cyclization reaction can also proceed over the active external surface of HZSM-5 and mordenite. With the increase of autoclavation temperature and pressure the yield of the cyclized products was increased. At high reaction temperature octahydroacridine increased and octahydrophenanthridine decreased. The reaction of cyclohexanone, formaldehyde and ammonia was also carried out using continuous-flow, fixed-bed reactor at 1 atm pressure. The vapour phase reaction was carried out at 400°C reaction temperature with 0.5 h 1 weight hourly space velocity using H-MCM-41 catalyst. The selectivities for octahydroacridine were 36.3, 33.5 and 36.9 percent at 85.4, 94.0 and 86.3 percent conversions of cyclohexanone over LaMCM-41, Cu-MCM-41 and Cr-MCM-41 respectively. The various parameters like catalyst, variation of reactants, reaction temperature, etc. were studied. Under and similar to the supercritical conditions, there is substantial increase in the reactive collisions miscibility is increased, the mass transfer and heat transfer effect are enhanced, resulting into the increased yield and enhance the selectivity by using active and selective zeolite/molecular sieve catalysts. The varieties of heterocyclic compounds of acridine-type (three-fused ring system) or bis-annelated pyridines are obtained. The attempts are being made to synthesize useful compounds like tacrine (a drug for Alzheimer disease).