Synthesis of alkyl-5H-cyclopenta[b]pyrazines (author's transl)]

Synthesis of alkyl-5H-cyclopenta[b]pyrazines. Alkyl-5H-cyclopenta[b]-pyrazines (sometimes together with 5-alkylidene-5H-6,7-dihydrocyclopenta[b]pyrazines) are prepared by thermal degradation of 5-acetoxy-5H-6,7-dihydrocyclopenta[b]pyrazines; these are obtained by treatment of alkyl-5H-6,7-dihydrocyclopenta[b]pyrazine N-oxides with acetic anhydride. Cyclopenta[b]pyrazines which are potentially present in roasted food flavors possess interesting organoleptic properties.     

Microwave‐assisted synthesis of new regioisomeric 6,7‐dihydroindeno[1,2‐e]pyrimido[4,5‐b][1,4]diazepin‐5(5aH)‐ones

Novel 11‐amino‐6‐aryl‐6,7‐dihydroindeno[1,2‐e] pyrimido[4,5‐b][1,4]diazepin‐5(5aH)‐ones 4a‐f were prepared regioselectively by the tricomponent reaction of 4,5,6‐triaminopyrimidine 1, 1,3‐indandione 2 and aromatic aldehydes 3a‐f. The bicomponent approach, using 2,4,5,6‐tetraaminopyrimidine 5 and 2‐aryl‐ideneindandiones 6a‐f as reagents, afforded 9,11‐diamino‐6‐aryl‐6,7‐dihydroindeno[1,2‐e]pyrimido[4,5‐b]‐[1,4]diazepin‐5(5aH)‐ones 7a‐f in good yields and the regioisomeric 8,10‐diamino derivatives 8a‐c in lower yields. Both, bi‐ and tricomponent approaches were performed by microwave irradiation and all products were fully characterized by detailed NMR measurements.