Synthesis of 2-Methoxy-3H-Azepine Derived Compounds Through the Thermal Reaction between Alkylnitrobenzene and Tributylphosphine

Abstract

ABSTRAKReaksi fotolisis fenilazida telah banyak dilaporkan menghasilkan 3H-azepina, sedangkan metode reaksi termal dengan menggunakan turunan alkilnitrobenzena masih belum banyak diketahui. Sintesis senyawa baru turunan 2-metoksi-3H-azepina telah dilakukan dengan mereaksikan alkilnitrobenzena dan tributilphosphina (Bu3P) pada suhu 150°C selama 24 jam dalam pelarut metanol. Hasil analisis menunjukkan reaksi antara m-nitrobenzena menghasilkan dua isomer azepina yaitu 2-metoksi-6-metil-3H-azepina dan 2-metoksi-4-metil-3H-azepina sebanyak 61%. Reaksi 2,3-dimetilnitrobenzena dengan metode yang sama menghasilkan tiga isomer yaitu 2-metoksi-6,7-dimetil-3H-azepina; 2-metoksi-3,4-dimetil-3H-azepina dan 7-metoksi-5,6-dimetil-4H-azepina. Sedangkan reaksi antara 3,5-dimetilnitrobenzena hanya menghasilkan 2-metoksi-4,6-dimetil-3H-azepina sebanyak 42%. Reaksi antara 2,6-dimetilnitrobenzena tidak menunjukkan terbentuknya turunan 3H-azepina karena halangan sterik dari gugus metil pada posisi C2 dan C6. Elusidasi struktur dari semua senyawa baru turunan azepina yang disintesis telah dikonfirmasi menggunakan HETCOR.Kata kunci : azepina, siklisasi, reaksi intramolekular, fotolisis, tributilphosphina, nitrobenzena. ABSTRACTAlthough photolysis of phenyazide has been widely reported to give 3H-azepine, the thermal deoxygenation reaction of alkylnitrobenzene derived similar products hitherto unexplored. Novel synthesis of 2-methoxy-3H-azepine derivatives was carried out using alkylnitrobenzene with tributylphosphine (Bu3P) reacted at 150°C for 24 hours in the presence of methanol. Reaction of m-nitrobenzene with the above methods gave two isomers of 3H-azepine, namely, 2-methoxy-6-methyl-3H-azepine and 2-methoxy-4-methyl-3H-azepine in 61%. Reaction of 2,3-dimethylnitrobenzene with Bu3P afforded the three isomers, that is, 2-methoxy-6,7-dimethyl-3H-azepine; 2-methoxy-3,4-dimethyl-3H-azepine and 7-methoxy-5,6-dimethyl-4H-azepine. Reaction of 3,5-dimethylnitrobenzene gave the sole product of 2-methoxy-4,6-dimethyl-3H-azepine in 42%. In contrast, reaction of 2,6-dimethylnitrobenzene didn't give any product because the steric effect of methyl groups attached on C2 and C6. Structure elucidation of all novel products have confirmed by HETCOR.