Simultaneous Formation and Functionalization of Aryliminophosphoranes Using 1,3-Dihydro-1H-benzimidazol-2-ones as Precursors

Abstract

An atom-and step-economic synthesis of aryliminophosphoranes bearing ortho urea was achieved via unprecedented Ph 3 P-I 2 mediated ring-opening of 1,3-dihydro-1H-benzimidazol-2-ones with secondary amines. Tandem aza-Wittig/heterocyclization of the functionalized aryliminophosphoranes upon treatment with isothiocyanates enables a facile access to a single regioisomer of N 1 -substituted 2-aminobenzimidazoles as well as fused tetracyclic quinazolinone derivatives in one-pot. 31 P{ 1 H} NMR studies suggested that the urea C−N bond of benzimidazolone is weakened by N-phosphorylation, leading to aminolysis rather than the expected deoxygenative amination.

Efficient and Sustainable Electrosynthesis of N-Sulfonyl Iminophosphoranes by the Dehydrogenative P–N Coupling Reaction

“… First, iodide is oxidized at the anode to form I 2 and I 3 – . Then, phosphine I reacts with I 2 equivalent to form intermediate II , analogously to Kirsanov reactions. ,, This hypothesis is supported by a control experiment in which I 2 (1.0 equiv) instead of electric current was employed as the oxidizing agent (see the Supporting Information). Nucleophilic attack by sulfonamide III , followed by elimination of iodide and deprotonation, yields iminophosphorane IV .…”

“…Conventionally, iminophosphoranes can be synthesized through Staudinger reduction − or by reacting phosphines with iminoiodanes (Scheme a,b). − Alternatively, Kirsanov , − Appel -type, − or Mitsunobu -type − reactions can be performed to generate an electrophilic phosphine intermediate in situ, which is then trapped by the nitrogen precursor (Scheme c–e).…”

Synthesis of Tetracyclic Benzazole–Condensed Quinazolinones through Triphenylbismuth Dichloride Assisted Cyclodesulfurization

“…6 Phakhodee et al used benzamides to perform a tandem aza-Witting reaction and heterocyclization of 2-isothiocyanatobenzoate with aryliminophosphoranes, which were prepared from 1,3-dihydrobenzimidazol-2-ones and secondary amines, by using a triphenylphosphine–iodine system in the presence of triethylamine. 7 However, these protocols (Scheme 1 ) have several drawbacks in terms of heating requirement, limited substrate scope, and unclear key precursors due to tandem reactions.…”

“…NMR (100 MHz, CDCl 3 ):  = 112.2 (CH), 117.8 (C), 118.5 (C), 119.1 (CH), 125.9 (CH), 127.1 (CH), 127.4 (CH), 127.7 (C), 129.8 (CH), 135.6 (CH), 143.8 (C), 147.4 (C), 151.9 (C), 159.1 (C).MS (EI): m/z (%) = 314 (100) [M + ], 207 (18), 179 (18), 152(7), 130(9), 102(12).HRMS (ESI): m/z [M+ ] calcd for C 14 H 7 BrN 2 O 2 : 313.9691; found: 313.9687. mg (95%); colorless prisms; mp 234-235 °C (from hexane-CH 2 Cl 2 ); R f = 0.4 (EtOAc-hexane 2:8). IR (KBr): 3092, 1705, 1559, 1497, 1466, 1346, 1261, 1165, 1055, 893, 773 cm -1 .…”

Recent Advances in the Synthesis of Heterocycles by the Aza-Wittig Reaction

“…In 2020, Phakhodee and co-workers used 1,3-dihydro-2H-benzimidazol-2-ones 163 as precursors for the production of aryliminophosphoranes 164 (Scheme 43). 45 Reaction of 1,3-dihydro-2H-benzimidazol-2-ones 163 with iodine and Ph 3 P (20) followed by addition of various secondary amines 46 gave a wide range of iminophosphoranes 164 in poor to excellent yields.…”