Masahiro Egi

Cationic gold(I)-mediated intramolecular cyclization of 3-alkyne-1,2-diols and 1-amino-3-alkyn-2-ols: a practical route to furans and pyrroles.

The intramolecular cyclizations of the 3-alkyne-1,2-diols and the 1-amino-3-alkyn-2-ols with a low catalyst loading (0.05-0.5 mol %) of (Ph(3)P)AuCl-AgNTf(2) or (Ph(3)P)AuCl-AgOTf proceeded at room temperature to provide a variety of substituted furans and pyrroles in excellent yields (85-98% yields). This method is also fully applicable to the conversion of several dozen grams of the substrate using only 0.05 mol % each of the Au and Ag catalysts.

Mo−Au Combo Catalysis for Rapid 1,3-Rearrangement of Propargyl Alcohols into α,β-Unsaturated Carbonyl Compounds

The combination of Mo and cationic Au catalysts dramatically accelerated the rearrangement of diverse propargyl alcohols, which includes a short reaction time, mild conditions, and high product yields. A practical application to the highly challenging primary propargyl alcohols and the N-alkynyl amides is achieved.

One-Pot Synthesis of Optically Active Allyl Esters via Lipase−Vanadium Combo Catalysis

The combination of vanadium-oxo compounds (3 or 4) with a lipase produced the regio- and enantioconvergent transformation of racemic allyl alcohols (1 or 2) into optically active allyl esters. In this system, the vanadium compounds catalyzed the continuous racemization of the alcohols along with the transposition of the hydroxyl group, while the lipase effected the chemo- and enantioselective esterification to achieve the dynamic kinetic resolution.

Synthesis of biaryl compounds through three-component assembly: ambidentate effect of the tert-butyldimethylsilyl group for regioselective Diels-Alder and Hiyama coupling reactions.

The biaryl moiety is ubiquitous in natural products, pharmaceuticals, polymers, sensors, and in ligands for transition-metal catalysts. A number of useful methods for the preparation of these compounds have been developed based on the transition-metal-catalyzed cross-coupling of aryl halides with aryl metal species through Stille, Suzuki, Negishi, and Hiyama reactions. Multicomponent assembly protocols have been recognized as a powerful means for the preparation of molecular complexity and diversity, and are thus particularly suited for combinatorial chemistry and diversity-oriented synthesis. As an approach towards this goal, we now report the novel preparation of multisubstituted unsymmetrical biaryl compounds through the assembly of the following three components: a silylated benzyne, a furan derivative, and an aryl iodide [Eq. (1)]. Thus, this methodology involves the construction of silylnaphthalene derivatives by a regioselective Diels–Alder reaction of 3-tert-butyldimethylsilylbenzynes (3-TBDMS-benzynes) with furan derivatives followed by a Hiyama cross-coupling reaction of the generated TBDMSsubstituted cycloadducts with aryl iodides. We initially examined the Diels–Alder reaction of 3-phenylbenzyne (3a, R=Ph, R=H), generated in situ by treatment of 2-bromo-6-phenylphenyl triflate (1a) with nBuLi at 78 8C, and 2-tert-butylfuran (2a) to synthesize a multisubstituted biaryl compound. However, the regioselectivity of the reaction was quite low and afforded a 1:1.3 mixture of the head-to-tail (anti) and the head-to-head (syn) cycloaddition products 4a (Table 1, entry 1). We devised

Cationic Gold(I)-Catalyzed Intramolecular Cyclization of γ-Hydroxyalkynones into 3(2H)-Furanones

The combination of (p-CF(3)C(6)H(4))(3)PAuCl and AgOTf generates a powerful catalyst for the intramolecular cyclizations of readily available gamma-hydroxyalkynones under mild conditions. The substituted 3(2H)-furanones are obtained in 55-94% yields. This method is also applicable to the preparation of 2,3-dihydro-4H-pyran-4-ones.

Heteropolyacid-Catalyzed Direct Deoxygenation of Propargyl and Allyl Alcohols

The combination of H(3)[PW(12)O(40)]·nH(2)O (1 mol %) and Et(3)SiH led to the direct catalytic deoxygenation of propargyl alcohols, in which proper solvent selection Cl(CH(2))(2)Cl vs CF(3)CH(2)OH was the key to obtaining better product yields. Under similar conditions, the deoxygenation of allyl alcohols proceeded to give thermodynamically stable alkenes with migration of the double bonds in good yields.

Hypervalent iodine(III) induced intramolecular cyclization of substituted phenol ethers bearing an alkyl azido sidechain–a novel synthesis of quinone imine ketals

A novel and efficient synthesis of quinone imine ketals from substituted phenol ethers bearing an alkyl azido sidechain using a hypervalent iodine(III) reagent, phenyliodine(III) bis(trifluoroacetate)(PIFA), is described.

Efficient Intramolecular Cyclizations of Phenoxyethynyl Diols into Multisubstituted α,β-Unsaturated Lactones

AgOTf-catalyzed intramolecular cyclization of phenoxyethynyl diols proceeded under mild conditions to afford the multisubstituted α,β-unsaturated-γ-lactones in 55-98% yields. This method was also applicable to the synthesis of α,β-unsaturated-δ-lactones. A similar cyclization proceeded when AgOTf was replaced with a stoichiometric amount of N-bromosuccinimide to furnish the α-bromo-substituted α,β-unsaturated lactones.

Total synthesis of sulfur-containing pyrroloiminoquinone marine product, (±)-makaluvamine F using hypervalent iodine(III)-induced reactions

The first total synthesis of potent cytotoxic makaluvamine F 1, a sulfur-containing pyrroloiminoquinone marine product, has been accomplished using hypervalent iodine(III)-induced reactions.

Novel and efficient synthesis of sulfur-containing heterocycles using a hypervalent iodine(III) reagent

A novel and efficient synthesis of sulfur-containing heterocycles from phenol ethers bearing an alkyl sulfide sidechain using a combined reagent of a hypervalent iodine(III) species and BF3·Et2O is described.