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Reactive acyl trifluoromethanesulfonates are formed from the reaction of acyl fluorides with trimethylsilyl trifluoromethanesulfonate (TMSOTf). These electrophiles undergo Friedel–Crafts reactions with electron-rich aromatics at room temperature. When a sulfur atom is present at their γ position, their cyclization to acylsulfonium cations is observed and is followed by a rearrangement leading to benzothiepinones (or dibenzo[b,e]thiepinones) in 40–85% yield.

The feasibility of the cyclization of γ-alkylthiobutyric acid derivatives to form previously unknown five-membered-ring acyl sulfonium cations was studied. Experimental results were in good agreement with our DFT calculations that predicted such cyclizations to be easy if starting with acyl iodides and mixed anhydrides of triflic acid. Particularly efficient were the reactions of γ-alkylthiobutyryl fluorides with trimethylsilyl triflate in CDCl3 solution, which led to cyclic acyl sulfonium triflates. In some cases, the observed acyl sulfonium salts were stable enough to be characterized by NMR spectroscopy. They were found to be both alkyl-transfer reagents and acylating agents. They react with amines to form amides. These findings lend some weight to our hypothesis that the acyl sulfonium derived from methionine may have played a major role in the prebiotic synthesis of the first peptides on the primitive Earth.

A stereoselective synthesis of the spirolactam fragment (C31–C41) of a highly-potent immunosuppressant sanglifehrin A is described. The key steps involved in this synthesis are a desymmetrization protocol, Sharpless asymmetric epoxidation, Crimmins syn aldol reaction, Barton–McCombie deoxygenation, and acid-mediated spirolactamization.

Life developed on Earth probably about 3.8 billion years ago, on a planet that was already largely covered by oceans and where the atmosphere was very humid. The reactions, which may have led to the formation of the first polymers, particularly to the first peptides and nucleic acids, must have been compatible with these conditions. This is the case of the reaction of nitriles with aminothiols, such as cysteine and homocysteine. Since aminonitriles are the probable precursors of amino acids, this condensation reaction has been able to rapidly yield dipeptides, tripeptides, oligomers and even true polymers, each containing thiol functions. These thiol-rich peptides (TRP's) would then have assumed the various catalytic roles that the peptides containing cysteine residues play today. They allowed a rapid bloom of life in the primitive ocean. In this scenario, RNA's are not the first polymers, but have been synthesized, like DNA's, thanks to the catalytic properties of thiols in a mostly TRP world. In this world, due to its ability to form a thiolactone, homocysteine may have played the leading role in enabling the previously formed oligomers to be stappled together, thus accelerating the formation of long peptide chains.

A tandem cycloisomerization/Friedel–Crafts alkylation of indoles has been achieved in a one-pot process to produce 2,5-disubstituted furans using gallium-catalyzed sequential nucleophilic addition onto metal-activated 1-alkynyl-2,3-epoxy acetates. The reaction proceeds efficiently under mild conditions with complete regioselectivity to afford the substituted furan derivatives in good yields with high diversity.

A highly stereoselective total synthesis of an aliphatic depside (+)-bourgeanic acid via (-)-hemibourgeanic acid and bourgeanic lactone is described. The key steps involved in this synthesis are desymmetrization of bicyclic olefin with Brown's asymmetric hydroboration, Gillman's reaction, TEMPO-BAIB mediated selective oxidation of 1,3-diol, Yamaguchi macro-lactonization and LiOH-mediated partial hydrolysis of unusually stable eight-membered cyclic dilactone.

1,3-Diaryl propargyl alcohols undergo smooth intramolecular Friedel-Crafts cyclization with triethylsilane in the presence of 10 mol % iodine 3-aryl-1H-indene derivatives in good yields in short reaction times. This is the first example on the synthesis of substituted indenes from 1,3-diaryl propargyl alcohols. The use of inexpensive and readily available molecular iodine makes this method quite simple, more convenient, and practical.

The stereoselective total synthesis of spiroketal natural product (+)-aculeatin D and unnatural (+)-6-epi-aculeatin D has been accomplished. Sharpless kinetic resolution of secondary allylic alcohol and phenyliodine(III) bis(trifluoroacetate) (PIFA)-mediated oxidative spirocyclization were used as key steps in this synthesis.

The total synthesis of (10S,12S)-10-hydroxy-12-methyl-1-oxacyclododecane-2,5-dione is described proving the versatility of the Prins cyclization in natural products synthesis. The approach is convergent and highly stereoselective. Prins cyclization, esterification, ring-closing metathesis and oxidation reactions are utilized as key steps in the synthesis of this macrolactone.

Various 1,3-dicarbonyl compounds reacted readily with benzylic and propargylic alcohols in the presence of 10 mol % of phosphomolybdic acid supported on silica gel (PMA/SiO 2 ) under mild reaction conditions to produce 2-benzylic- and 2-propargylic-1,3-dicarbonyl compounds in excellent yields and with high selectivity.

Propargylic alcohols undergo smooth deoxygenative allylation with allylsilanes in the presence of a solution of 10 mol % of copper(II) tetrafluoroborate in acetonitrile to afford the corresponding 1,5-enynes in good to high yields under mild and neutral conditions. Scandium triflate is also found to catalyze efficiently the nucleophilic substitution of propargylic alcohols with allylsilanes.

A variety of heteroaromatic compounds such as indole, carbazole, pyrrole, and furan underwent smooth coupling with propargylic alcohols in the presence of 10 mol% of indium(III) bromide under mild conditions to furnish exclusively propargylated heterocycles in excellent yields and high regioselectivity. The use of indium(III) bromide makes this procedure simple, convenient, and practical. The hydroxy groups of the propargylic alcohols were simply replaced by the nucleophiles in an S N 2′ manner.

Since methionine is capable of self-activation, the dipeptides formed by the reaction of its activated form with another amino acid were over-represented in the primitive ocean. This hypothesis giv...

The cyclic 1,3-dicarbonyl compounds undergo smooth cyclization with aryl propargyl alcohols in the presence of 10 mol % indium tribromide in refluxing dichloroethane to produce 2,4-diarylpyran derivatives in good yields with high selectivity.

A tandem cycloisomerization/Friedel–Crafts alkylation of indoles has been achieved in a one-pot process to produce 2,5-disubstituted furans using gallium-catalyzed sequential nucleophilic addition onto metal-activated 1-alkynyl-2,3-epoxy acetates. The reaction proceeds efficiently under mild conditions with complete regioselectivity to afford the substituted furan derivatives in good yields with high diversity.

Attempted deoxygenation of diaryl-substituted propargyl alcohols according to A) unexpectedly results in a tandem isomerization/reduction followed by intramolecular Friedel—Crafts-type cyclization to produce indene derivatives An exclusive formation of vinyl iodides (X) is observed if the propargylic alcohol moiety bears an alkyl group.

The cyclic 1,3-dicarbonyl compounds undergo smooth cyclization with aryl propargyl alcohols in the presence of 10 mol % indium tribromide in refluxing dichloroethane to produce 2,4-diarylpyran derivatives in good yields with high selectivity.

Various 1,3-dicarbonyl compounds reacted readily with benzylic and propargylic alcohols in the presence of 10 mol % of phosphomolybdic acid supported on silica gel (PMA/SiO 2 ) under mild reaction conditions to produce 2-benzylic- and 2-propargylic-1,3-dicarbonyl compounds in excellent yields and with high selectivity.

Propargylic alcohols undergo smooth deoxygenative allylation with allylsilanes in the presence of a solution of 10 mol % of copper(II) tetrafluoroborate in acetonitrile to afford the corresponding 1,5-enynes in good to high yields under mild and neutral conditions. Scandium triflate is also found to catalyze efficiently the nucleophilic substitution of propargylic alcohols with allylsilanes.

A variety of heteroaromatic compounds such as indole, carbazole, pyrrole, and furan underwent smooth coupling with propargylic alcohols in the presence of 10 mol% of indium(III) bromide under mild conditions to furnish exclusively propargylated heterocycles in excellent yields and high regioselectivity. The use of indium(III) bromide makes this procedure simple, convenient, and practical. The hydroxy groups of the propargylic alcohols were simply replaced by the nucleophiles in an S N 2′ manner.

Indoles undergo smooth alkylation with propargylic acetates in the presence of Amberlyst A-15® under mild conditions to produce 3-propargylated indoles in excellent yields with high selectivity. This is the first example for the alkylation of indoles with propargylic acetates using the acid catalyst.

Indoles undergo smooth alkylation with propargylic alcohols in the presence of 10 mol % of scandium triflate under mild conditions to produce 3-propargylated indoles in excellent yields with high selectivity.