A unique site-selective reaction of ketones with new recyclable hypervalent iodine(III) reagents based on a tetraphenylmethane structure

We have synthesized new recyclable reagents having a tetraphenylmethane backbone and used them in the site-selective alpha-tosyloxylation of ketones.     

Direct synthesis of bipyrroles using phenyliodine bis(trifluoroacetate) with bromotrimethylsilane

[reaction: see text] The hypervalent iodine(III) reagent, phenyliodine bis(trifluoroacetate) (PIFA), mediates the unprecedented, oxidative coupling reaction of pyrroles to give alpha-linked bipyrroles selectively in the presence of bromotrimethylsilane. This straightforward synthesis could provide 2,3'-bipyrrole by the choice of a N-substituent of pyrrole. Mechanistic consideration of the present reaction is also described.     

Highly Active Catalysts for the Transfer Dehydrogenation of Alkanes: Synthesis and Application of Novel 7–6–7 Ring‐Based Pincer Iridium Complexes

A series of Ir–PCP pincer precatalysts [(7–6–7‐^RPCP)Ir(H)(Cl)] and [(7–6–7‐^ArPCP)Ir(H)(Cl)(MeCN)] bearing a novel “7–6–7” fused‐ring skeleton have been synthesized based upon the postulate that the catalytic species would have durability due to their rather rigid structure and high activity owing to the low but sufficient flexibility of their backbones, which are not completely fixed. Treatment of these precatalysts with NaOtBu gave rise to the active 14 electron (14e) species [(7–6–7‐^iPrPCP)Ir] and [(7–6–7‐^PhPCP)Ir], which can trap hydrogen and were spectroscopically characterized as the tetrahydride complexes. Both [(7–6–7‐^iPrPCP)Ir] and [(7–6–7‐^PhPCP)Ir] were found to be highly effective in the transfer dehydrogenation of cyclooctane with tert‐butylethylene as the hydrogen acceptor, the initial reaction rate at high temperature (230 °C) being higher for [(7–6–7‐^iPrPCP)Ir] than [(7–6–7‐^PhPCP)Ir], and the turnover number (TON) of the overall hydrogen transfer being higher for the latter. Nonetheless, the estimated TONs were as high as 4600 and 4820 for the two complexes at this temperature, respectively, which are unprecedented absolute values. In terms of durability, the [(7–6–7‐^PhPCP)Ir] complex is the catalyst of choice for this reaction. Structural analysis and computational studies support the importance of the low flexibility of the ligand core.     

Total synthesis of macrosphelide A by way of palladium-catalyzed carbonylative esterification

We achieved the total synthesis of macrosphelide A, as part of a combinatorial library of its analogues. The key intermediate, the seco-acid derivative, was prepared from the corresponding vinyl iodide using sequential carbonylative esterification.     

New synthesis of spirocycles by utilizing in situ forming hypervalent iodine species

A very effective spirocyclization procedure for installing nucleophiles (Nu = N(3), NO(2), SCN, SO(2)Tol, and halogens) via iodonium(III) salts has been developed using the combination of iodoarene and mCPBA. The high-yielding syntheses of the cyclohexadienone-type spirocyclic compounds 2 having varied functionalities in the skeletons have been achieved from the aryl alkynes 1 with the optimized bis(iodoarene) 3h.     

Metal-free C-H cross-coupling toward oxygenated naphthalene-benzene linked biaryls

The intermolecular C-H cross-coupling between aromatic ethers has been achieved for the first time using perfluorinated hypervalent iodine(III) compounds as extreme single-electron-transfer (SET) oxidants. The demonstrations of this specific coupling could provide a direct route to valuable oxygenated mixed naphthalene-benzene biaryls 3 only, without formation of other biaryl-derived byproducts.     

Controlled couplings of quinone monoacetals using reusable polystyrene-anchored specific proton catalyst

Controlled couplings of quinone monoacetals 1 with soft nucelophiles have been achieved using a new and reusable perfluorobenzoic acid (PFBA) immobilized on polystyrene beads as an efficient polymer-anchored specific proton. Various advantages regarding the recovery, reusability, and reproducibility as well as the high chemoselectivity toward quinone monoacetals 1 have been determined as the key features of the cleaner systems with newly developed solid acid promoter for the reactions.