Dibromotriphenylphosphorane promoted synthesis of condensed heterocyclic systems from aromatic diamines

Abstract

A new and rather widely applicable method for the synthesis of a number of tri, tetra‐, and pentacyclic compounds from ortho‐aminodiacylarylimides and dibromotriphenylphosphorane via an intramolecular cyclization is reported. A mechanism for this cyclization is proposed.

Practical Alternative Synthesis of 1-(8-Fluoro-naphthalen-1-yl)piperazine

“…Initial attempts of diazotization of 14 with 1 equiv of sodium nitrite in hydrogen fluoride–pyridine did not give any desired product. Considering the possible interference of the second amino group during the diazotization, protection of one of the amino groups of 14 with succinic anhydride or phthalic anhydride was carried out according to literature . However, diazotization of both monoprotected derivatives under either aqueous or nonaqueous conditions gave mostly unreacted starting material.…”

A Novel, Domino Synthesis of Tricyclic Benzimidazole Derivatives Using Continuous Flow

“…Surprisingly, significant ring opening takes place producing 7 (31 %). Based on this experience we concluded that there is equilibrium between the lactam (9) and the open chain (7) forms. Starting from compound 12, a small amount of ring opening product was observed (entry 10, 11 % 8).…”

“…Furthermore, it can be said that longer residence time (Table 4, entry 18, 32 min, 35 % 9), and greater anhydride excess (Table 4, entry 20, 6 eq. 16, 47 % 9), resulted in the formation of more lactam type product (9). We assumed, that the main reason of side reactions is the residual 2-hydroxy compound (18, Fig.…”

“…The ring closure can be carried out via an intramolecular aza-Wittig reaction using phosphorus, arsenic, boronic or antimony phosphorane reagents [9][10][11]. Starting from benzimidazole-2-propanoic acid (4, Path C) the desired product (1) can be obtained with a dehydration step which feasibly with pyrolysis reaction [9] or with using acetic anhydride or thionyl chloride [12]. There is only a few example known in the literature, when the synthesis of 1 was implemented through nitro group reduction starting from 3b (Fig.…”

11H-isoindolo[2,1-a]benzimidazoles (Review)

“…A method was proposed for the synthesis of the partially hydrogenated isoindolobenzimidazolone 33 by the Wittig aza reaction (yield 48%) [35]:…”