Platinum-Catalyzed Intramolecular Hydroarylation of Allenyl Arenes: Efficient Synthesis of 1,4-Dihydronaphthalenes

Diversified Reactivity of Triphenylphosphine: Reinvestigation of the Phosphine-Mediated Reductive Condensation Approach for the Synthesis of Substituted Furans

A reinvestigation of "Phosphine-Mediated Reductive Condensation of γ-Acyloxy Butynoates: A Diversity Oriented Strategy for the Construction of Substituted Furans" (J. Am. Chem. Soc. 2004, 126, 4118-4119) revealed different chemoselectivity of triphenylphosphine in the reactions with the γ-acyloxy butynoate substrates of varying substitution patterns/electronics. Furthermore, the electronics of the triaryl phosphine reagent could be tuned to trap a putative intermediate such as A, leading to the semihydrogenation of propiolamide substrates.

Metal-free intramolecular hydroarylation of alkynes

An efficient metal-free intramolecular hydroarylation reaction of alkynes is described here. A series of aryl and N-group attached alkynes generated the intramolecular hydroarylation products in high yields.

Gold(I)-Catalysed Hydroarylation of 1,3-Disubstituted Allenes with Efficient Axial-to-Point Chirality Transfer

Hydroarylation of enantioenriched 1,3-disubstituted allenes has the potential to proceed with axial-to-point chirality transfer to yield enantioenriched allylated (hetero)aryl compounds. However, the gold-catalysed intermolecular reaction was previously reported to occur with no chirality transfer owing to competing allene racemisation. Herein, we describe the development of the first intermolecular hydroarylations of allenes to proceed with efficient chirality transfer and summarise some of the key criteria for achieving high regio- and stereoselectivity.

Fe(OTf)3-catalysed Friedel-Crafts reaction of benzenoid arenes with α,β-unsaturated carbonyl compounds: easy access to 1,1-diarylalkanes

A simple and efficient method for the synthesis of 1,1-diarylalkanes via the Friedel-Crafts-type alkylation reaction of electron-rich arenes with cinnamic acid ester derivatives or chalcones is reported. Iron triflate has been found to be the best catalyst for the Friedel-Crafts-type alkylation reaction with α,β-unsaturated carbonyl compounds. This reaction afforded β,β-diaryl carbonyl compounds in good yields (65-93%) and with excellent regioselectivities. Remarkably, this method is also compatible with a variety of indoles to provide 3-indolyl-aryl carbonyl compounds in excellent yields. Great efforts have been made to deduce a plausible reaction mechanism based on isotopic labelling experiments.

Asymmetric Construction of Six-Membered Rings by Cyclization of Allenes with Dinuclear Gold Catalysis

A simple and efficient method for the synthesis of 1,4-dihydroarenes by gold-catalyzed 6-endo cyclization of benzylic allenes has been developed. Furthermore, asymmetric hydroarylation of enantioenriched allenes has been realized to offer a practical and convergent approach to aromatic ring-fused six-membered cycles containing a chiral stereocenter such as 1,4-dihydronaphthalenes, 1,4-dihydrodibenzo[b,d]thiophenes, and 4,7-dihydrobenzo[b]thiophenes by applying dinuclear [(dppm)Au2 Cl2 ] [dppm=methylenebis(diphenylphosphane)] combined with AgOTf as the catalyst to ensure the high efficiency of chirality transfer. ESI-MS has been applied to characterize some of the key reactive dinuclear gold intermediates successfully.

Lewis acid-promoted cyclization/halogenation of allenyl ethenetricarboxylates and the corresponding amides: stereoselective synthesis of haloalkenyl five-membered heterocycles

Lewis acid-promoted intramolecular reactions of allenyl ethenetricarboxylates and the corresponding amides have been examined. Reactions of allenyl ethenetricarboxylates and the amides with Lewis acids such as AlCl3, AlBr3 and ZnX2 (X = Cl, Br, I) gave 3,4-trans haloalkenyl five-membered heterocycles stereoselectively. The stereochemistry was determined by NOE experiments and reduction of the cyclized products. Various transformations of the haloalkenyl functionalized cyclic compounds have also been performed.

Electrophilic activation of allenenes and allenynes: analogies and differences between Brønsted and Lewis acid activation

This review focuses on electrophilic activation of allenes by an acid. Key mechanistic features are presented together with recent synthetic applications.

Gold(i)- and platinum(iv)-catalyzed intramolecular annulations of allenes towards furans

Intramolecular annulations of allenes towards furans to give six-membered ring fused furans with gold and platinum catalysts have been developed.