Iron-Catalyzed Synthesis of 13-Aryl-13H-indeno[1,2-l]phenanthrene via Double Annulations of 2-Alkynyl Biaryls.

An Fe(III)-catalyzed expedient synthesis of 13-aryl-13H-indeno[1,2-l]phenanthrene is described by a double annulations of 2-alkynyl biaryls, initiated by the activation of acetal. This strategy provides a simple, efficient and regioselective synthesis of varieties of indenophenanthrene derivatives from easily available starting materials under mild conditions in high to excellent yields. A plausible reaction mechanism is proposed.

Iron(III)-catalyzed synthesis of indole-xanthydrol hybrid through oxidative cycloisomerization/hydroxylation reaction.

An efficient one-pot synthesis of an indole-xanthydrol hybrid is described in the presence of catalytic combinations of Fe(NO3)3/FeCl3. This strategy involves a series of reactions such as allylic oxidation, isomerisation, cyclisation and hydroxylation reactions in a tandem manner. This protocol offers several advantages including mild reaction conditions, operational simplicity, high selectivity, good yields and easily accessible starting materials. The synthetic utility of this protocol was further demonstrated by the one-pot synthesis of the highly substituted xanthene containing bis-indolylmethane derivative. The preliminary mechanistic studies reveal that the reaction is initiated by the generation of radicals in the presence of catalytic iron(III)-salts.

Iron-catalyzed carboarylation of alkynes via activation of π-activated alcohols: rapid synthesis of substituted benzofused six-membered heterocycles.

An Fe(OTf)3-catalysed carboarylation of alkynes is reported for the straightforward synthesis of densely substituted 1,2-dihydroquinolines from N-propargyl anilides and π-activated alcohols. The reaction provides a new method for the synthesis of highly substituted benzofused six-membered heterocycles by the formation of two carbon-carbon bonds and one ring in a single step. The power of the methodology was further extended to the synthesis of substituted chromene and thiochromene derivatives in high yields. In addition, substituted quinoline derivatives were also achieved in a single step in the presence of FeCl3 through detosylation/aromatisation. A number of control experiments have been performed and a plausible mechanism has also been proposed to explain the formation of the products.

Application of the Povarov Reaction in Biaryls under Iron Catalysis for the General Synthesis of Dibenzo[a,c]Acridines.

A modified Povarov reaction involving 2'-alkynylbiaryl-2-carbaldehydes and aryl amines with tandem oxidation was performed using catalytic FeCl3. The outcome was an efficient general synthesis of dibenzo[a,c]acridines with moderate to high yields. This method offers simplicity in the preparation of substrates, diverse substrate scope, and high atom economy. The generality of the protocol was verified by synthesizing a tribenzo[a,c,h]acridine derivative. Photophysical properties of the synthesized compounds were also studied. The compounds absorb UV light typically in the range 230-330 nm and emit in the visible range of 400-420 nm.