Reactions of Zirconocene–1-Aza-1,3-diene Complexes with Acyl Cyanides: Substrate-Dependent Synthesis of Acyl- or Non-Acyl-Substituted Pyrroles

Abstract

Insertion of acyl cyanides into azazirconacyclopentenes derived from 1,3-azadienes has been described, which affords acyl-or non-acyl-substituted pyrroles upon acidic quenching. These reactions are initialized through CO insertion into the azazirconacycle to afford seven-membered oxaazazirconacycles. In the cases of 1,4-or 1,2,4-substituted azadienes, addition of a second molecule of acyl cyanide followed by cyclization upon acidic quenching leads to acyl-substituted pyrroles. In the cases of 1,3,4substituted azadienes, the addition of a second molecule of acyl cyanide cannot proceed due to the steric hindrance caused by the R 3 group on the zirconium intermediate. Acidic quenching of the resulting zirconium intermediate affords non-acyl-substituted pyrroles.

Reactions of Secondary Allylamines with Bis(η5:η1-pentafulvene)titanium Complexes: Selective Formation of Monoazabutadiene Titanium Complexes by N–H and C–H Bond Activation

“…Various coordination modes of monoazabutadiene ligands are known. − Group IV metallocene and non-metallocene type complexes are known to exhibit a characteristic envelope structure (Scheme ). ,− …”

Iridium-Catalyzed [2 + 2 + 2] Cycloaddition of Bithiophen-Linked Diynes with Nitriles: Scope and Mechanistic Study with Quantum Chemical Calculation

“…All solvents were dried and distilled before use by the usual procedures. [Ir­(cod)­Cl] 2 , nitrile 4f and 4i , diyne 1b , 2,2′-dibromo-3,3′-bithiophene, 4,4′-dibromo-3,3′-bithiophene, 3,3′-diiodo-2,2′-bithiophene, and 3,3′-dibromo-2,2′-bibenzo­[ b ]­thiophene were prepared as described in the literature. Nitriles 4a–4e , 4g , and 4h , alkynes 10a - 10c , isocyanate 12 , 1,2-bis­(diphenylphosphino)­ethane (DPPE), 1,2-bis­[bis­(pentafluorophenyl)­phosphino]­ethane (F-DPPE), (±)-2,2′-bis­(diphenylphosphino)-1,1′-binaphthalene ( rac -BINAP), 2,2′-bis­(diphenylphosphino)-1,1′-biphenyl (BIPHEP), 3,3′-dibromo-2,2′-bithiophene were purchased and used as received.…”