Reactions of 2-Benzoselenopyrylium Salts with Hydrazine: A New Easy Access to 5H-2,3-Benzodiazepines

Abstract

While the solvent-free reactions of the 2-benzoselenopyrylium salts (9) with methyl-or phenylhydrazine afforded the 1-hydrazino-1H-isoselenochromenes (11, 12), the treatment of the salts (9) with anhydrous hydrazine in dry acetonitrile resulted in a ring transformation to give the 5H-2,3-benzodiazepines (13) in one-pot under mild conditions in moderate yields.

Synthesis of Vinyl Selenides

“…o -Alkynylbenzyl selenols 104 , obtained from reaction of o -alkynylbenzyl bromide 105 with NaHSe or by the cleavage of the diselenide 106 with NaBH 4 /C 2 H 5 OH, easily cyclized to afford a mixture of the respective isoselenochromenes 107 and ( Z )-1-methylidene-2-selenaindanes 108 in 56−81% yields ( 107 : 108 ratio = 49:22 to 60:14, Scheme ). , The terminal o -ethynylbenzylselenol 104a regioselectively cyclized to isoselenochromene 107a in 56% yield. On the other hand, the phenyl substituted selenol 107b cyclized only via a 5- exo - dig reaction, giving only the benzylidene-2-selenaindane 108b in 66% yield.…”

“…In the same article, the authors prepared (Z)-1-organylteluro-2-phenylthio-1-organylethenes, using ). 58,59 The terminal o-ethynylbenzylselenol 104a regioselectively cyclized to isoselenochromene 107a in 56% yield. On the other hand, the phenyl substituted selenol 107b cyclized only via a 5-exo-dig reaction, giving only the benzylidene-2-selenaindane 108b in 66% yield.…”

Asymmetric Synthesis of Multifunctionalized 2,3-Benzodiazepines by a One-Pot N-heterocyclic Carbene/Chiral Palladium Sequential Catalysis

“…One of the most frequently used strategies to synthesize 2,3-benzodiazepine, dihydro- and tetrahydro-2,3-benzodiazepine, 2,3-benzodiazepin-4-one and 2,3-benzodiazepin-1,4-dione compounds is to construct the 2,3-benzodiazepine ring by means of the condensation reaction between a hydrazine or substituted hydrazines with the carbonyl compound including 1-( o -acyl)­aryl-2-ketones, , 2-( o -acyl)­arylacetic acids and esters, , and 2-( o -carboxy)­arylacetic acid anhydride . Other methods such as the Rh-catalyzed coupling reaction between N -boc hydrazones and diazoketoesters followed by intramolecular condensation, the ring expansion reaction of tetrahydrodiazirino­[3,1- a ]­isoquinoline with sulfonyl chlorides, and the reaction of hydrazine with 2-benzopyrylium or 2-benzoselenopyrylium salts have also been reported. Although most of the bioactive 2,3-benzodiazepine derivatives contain a stereogenic center, and different enantiomers have considerably different bioactivities on the physiologic system, − surprisingly, the asymmetric synthesis of chiral 2,3-benzodiazepine derivatives remains largely unexplored.…”

Comprehensive DFT and MP2 Level Investigations of Reaction of 2,3-Dihydro-1,5-benzodiazepine-2-thiones with Hydrazine

“…The recyclization of heterocyclic compounds in reactions with hydrazine and its derivatives has been extensively studied experimentally and has been shown to be very important in organic synthesis. − Despite numerous predictions of the possible mechanisms of the recyclization processes, theoretical verification for the proposed mechanisms by quantum mechanical calculations has not been yet accomplished. In a recent paper, we reported the theoretical investigation on hydrazinolysis of 4-methyl-2,3-dihydro-1,5-benzodiazepin-2-one leading to 3-methylpyrazolone-5.…”