A rapid, efficient and solvent‐free – green – protocol for Groebke–Bienaymé–Blackburn reaction (G−B‐B reaction) for the synthesis of fused‐imidazo heterocycles has been developed. The methodology reported here involves multi‐component reaction (MCR) catalyzed by reusable Yb(OTf)3 (a mild and water‐compatible Lewis acid) under microwave irradiation which allows fast and efficient preparation of the title compounds in excellent yield. The salient features of our protocol are solvent‐free, low catalyst loading (2.5–0.1 mol%) with good turnover number (TON: 890) and turnover frequency (TOF: 178/min), less reaction time (5 min), no dependency over specialized purification (by either column chromatography or recrystallization) and very high isolated yield (95–99 %) with excellent green chemistry metrics (E‐factor: 0.071 and Mass Intensity: 1.071). The water compatibility of the catalyst Yb(OTf)3 has been exploited for its efficient recovery through water washings. In addition, the other exciting milestones of the protocol are catalyst and workup solvent recycling, excellent conversion with notorious substrates such as enolizable aldehyde or isonitrile bearing reactive substituent, very efficient at higher scale (50 mmol) and easy to couple with other methods (one‐pot two‐step cyclization: G−B‐B reaction and Ullmann‐type coupling).

A rapid and elegant tandem azide–isocyanide cross‐coupling/cyclization protocol has been developed based on a nitrene transfer reaction. The palladium‐catalyzed ligand‐free methodology led to the synthesis of three different heterocyclic scaffolds with excellent atom/step/redox economy. Studies based on first‐principles‐based quantum calculations and control experiments unraveled a concerted process of nitrene transfer reaction on isocyanides, ruling out the metallaaziridine intermediate reported earlier. This finding could pave the way for novel applications of nitrene transfer reactions to generate bioactive heterocycles.magnified image

A rapid and efficient synthesis of aminotetrazole from aryl azides, isocyanides, and TMSN is developed. The reaction is promoted by sequential Pd(0)/Fe(III) catalysis. The reaction sequence utilizes the Pd-catalyzed azide-isocyanide denitrogenative coupling reaction to generate unsymmetric carbodiimide in situ, which reacts with TMSN in the presence of FeCl in a single pot. The methodology has distinct advantages over traditional synthetic approaches where toxic Hg and Pb salts are employed at stoichiometric scale.

No abstract

No abstract

No abstract

A metal free approach to access congested aryl amines using aza-oxyallyl cations as electrophiles has been reported. The given method could readily be adapted for the synthesis of coveted 3,5-benzodizepinones.

No abstract