A Concise Route to a Key Intermediate in the Total Synthesis of Sempervirine¹

Transformations of phenylhydrazones of 5‐acyl‐1,2,4‐triazines to pyrazolo[4,3‐e][1,2,4]triazines or 4‐cyanopyrazole

“…The required phenylhydrazones of 5-acyl-1,2,4-triazine 1a-l are directly available in high yield from the reaction of 5-acyl-3-methylsulfanyl-1,2,4-triazines (4) [8,9], with substituted phenylhydrazine hydrochlorides according to our previously published procedure (Scheme 2) [6]. In the initial experiment 1a (R 2 = H) has been subjected to reaction with twice excess of p-toluenosulfonic acid at 235 °C for 1 min.…”

New pyrazolo[4,3-e][1,2,4]triazine sulfonamides as carbonic anhydrase inhibitors

“…Next, triazine 2 was reacted according to literature procedure 23 with nitroethane in KOH/DMSO mixture at room temperature to give oxime 3 as a main product 24 which were converted into appropriate ketone 4, in good yield using literature procedure. 25 Ketone 4 was reacted with arylhydrazines according to literature description 26 to give appropriate hydrazones 5a-f as key intermediates for the construction of 1H-pyrazolo [4,3-e] [1,2,4]triazine derivatives 6a-f under intramolecular nucleophilic substitution reaction of hydrogen. 27,28 The low yield for the synthesis of derivative 6f prevented its further use in the preparation of sulfonamides.…”

Cycloalkenopyridines by ring transformations of diazines and triazines

“…9). 20 Similarly, reaction of 36a-c,e with 1-pyrrolidinocyclohexene 2(n=2) provides the corresponding 3-acyl-5,6,7,8-tetrahydroisoquinolines 39a-c,e. 20 The rate of the transformation is lower than the reaction with 1-pyrroldinocyclopentene, probably due to steric hindrance in the formation of the cyclohexenoadduct.…”

“…20 Similarly, reaction of 36a-c,e with 1-pyrrolidinocyclohexene 2(n=2) provides the corresponding 3-acyl-5,6,7,8-tetrahydroisoquinolines 39a-c,e. 20 The rate of the transformation is lower than the reaction with 1-pyrroldinocyclopentene, probably due to steric hindrance in the formation of the cyclohexenoadduct. It is of interest to mention that 3-acetyl-1-methylthio-5,6,7,8-tetrahydroisoquinoline 39e is a useful key intermediate in the Fisher preparation of 2(3-(5,6,7,8-tetrahydroisoquinolinyl))indole 40, the precursor in the synthesis of the zwitterionic indole alkaloid sempervirine 41 (Scheme 9).…”