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Direct heterocyclization of benzocrown ethers

“…Recently, we have demonstrated that activated arenes readily participate in tandem with heterocyclization involving isobutyraldehyde and nitriles with different properties [9]. Naturally, it was of great interest to us to apply this synthetic motif toward benzocrown ethers.…”

“…Evaporation of the solvent and recrystallization of a residue from hexane afforded 1.12 g (70%) of 9. Methylthio-6,7-(1 ,4 ,7 ,10 ,13 -pentaoxatridecylene)-3,3-pentamethylene-3,4-dihydroisoquinoline (9). mp 115.5-117.5…”

Synthesis and Antiinflammatory and Analgesic Activity of 2H-3,3-Dimethyl-3,4-dihydroisoquinolin-1-ones

“…The target product I was collected with a fraction boiling at 150 -160°C; yield, 1.9 g (77%); C 15 H 21 NS. Upon prolonged standing, the oil solidifies; double recrystallization of this solid from methanol yields pure thioester; m.p., 55 -56°C; yield 52%; IR spectrum (n max , cm -1 ): 1610, 1580, 1500; 1 1-Methylthio-3,3,6,7-tetramethyl-3,4-dihydroisoquinoline was synthesized as described in [3].…”

“…The initial 3,3-dialkhyl-3,4-dihydroisoquinolines were obtained using either a linear scheme (method A) [2] or a variant of three-component synthesis (method B) [3]. In the case of cumol, only the linear scheme was realized because the target product yield from a three-component synthesis was below 3 % that was probably related to protonation of the isopropyl group under the reaction conditions employed.…”

Nitrogen heterocycles from trimethylbenzenes

“…Several alternative methodologies were developed for the Ritter reaction [3,4], and the Ritter reaction was applied to the enan- tiospecific synthesis of 3-aza-bicyclic compounds [5], cis-fused hexahydro-4aH-indeno[1,2-b]pyridine ring system [6], and six-five-six fused-ring structures [7]. Recently, we have reported that the reaction of activated arenes with nitriles and isobutyric aldehyde in concentrated sulfuric acid gives 3,3-dimethyl-3,4-dihydroisoquioline derivatives [8,9].…”