Synthesis and properties of 1,2-diaryl-4,5,6,7-tetrahydro-1H-1,3-diazepines and 1,2-diaryl-1,4,5,6,7,8-hexahydro-1,3-diazocines. Comparison with the five- and six-membered homologues

Synthesis and properties of seven- to nine-membered ring nitrogen heterocycles. Cyclic amidines and cyclic amidinium salts

“…76 Phosphorus oxychloride, polyphosphoric acid (PPA), ethyl polyphosphate (PPE) and trimethylsilylpolyphosphate (PPSE) have been used as dehydrating agents for the synthesis of N-aryl five-to eightmembered cyclic amidines. 35,[78][79][80] The synthesis of medium-sized cyclic amidines through the cyclization of aminoamides was first reported in 1977 (Table 1, entries 1-6), 74 when a series of 1,2-diaryl-1,3-diazepines and diazocines having a nitrophenyl substituent on N-1 were synthesized through the ring closure of the corresponding N-nitroaryl-N'-aroyltetra-and penta-methylenediamines, respectively, employing a chloroform solution of PPE or phosphorus oxychloride as cyclizing agent for the synthesis of diazepines and neat PPE to obtain the corresponding diazocines. Similarly in 2000 Hedrera et al synthesized 1,3-diazepines employing the same cyclizing agent (Table 1, entries 7-10).…”

Polyphosphoric Acid Trimethylsilylester: A Useful Reagent for Organic Synthesis

“…The PPSE-promoted cyclodehydration of N-aryl-N'-benzoyltetramethylenediamines 81 gave considerable better yields for the preparation of 1H-4,5,6,7-tetrahydro-1,3-diazepines 82, 19,28 than those obtained when PPE was employed. 29,30 The authors attributed the longer reaction times for PPSE due, probably, to the stronger dehydration power of PPE.…”

An Efficient Synthesis of 2,3-Dihydro-1H-pyrimido[1,2-a]quinoxaline 6-Oxides

“…Melting points were taken on a Büchi capillary apparatus and are uncorrected. 1 6 and N-(o-nitrophenyl)-1,4-butanediamine 7 were described in the literature.…”