Masahito Murai

The current work describes the marked rate of acceleration caused by phosphine ligands on the rhodium-catalyzed dehydrogenative silylation and germylation of unactivated C(sp(3))-H bonds. The reactivity was affected by the steric and electronic nature of the phosphine ligands. The use of the bulky and electron-rich diphosphine ligand (R)-DTBM-SEGPHOS was highly effective to yield the dehydrogenative silylation products selectively in the presence of a hydrogen acceptor. An appropriate choice of

Use of a rhodium catalyst with electron-rich and bulky chiral diphosphine ligands having C2-symmetry allowed efficient dehydrogenative silylation of the C(sp(2))-H bond of ferrocenes leading to chiral benzosiloloferrocenes. The substrate scope was expanded to hydrogermane and hydrosilanes having a ruthenocene backbone, which resulted in a new approach to benzosilole- and benzogermole-fused metallocenes.

Mechanistic insight into the construction of quaternary silicon chiral centers by rhodium-catalyzed synthesis of spiro-9-silabifluorenes through dehydrogenative silylation is reported. The C2 -symmetric bisphosphine ligand, BINAP, was effective in controlling enantioselectivity, and axially chiral spiro-9-silabifluorenes were obtained in excellent yields with high enantiomeric excess. Monitoring of the reaction revealed the presence of a monohydrosilane intermediate as a mixture of two constitut

Azulene-fused polycyclic aromatic hydrocarbons (PAHs) were synthesized from commercially available azulene in four steps. The resulting azulene conjugates exhibited significantly narrow HOMO-LUMO bandgaps with high air stability, confirmed by photophysical study. Introduction of azulene also enabled the unique reversible stimuli-responsiveness even with the weak acid and base, which can potentially control the degree of conjugation and optoelectronic properties by simple acid-base and redox proc

The reaction of 2-(2-arylphenyl)vinyl ethers in the presence of a catalytic amount of bismuth(III) triflate gave substituted phenanthrenes in excellent yields under mild reaction conditions. The reaction was also applied to the construction of other polycyclic aromatic hydrocarbons (PAHs), such as chrysene, helicene, and pyrene having a phenanthrene backbone, via regioselective cyclization. This method has the advantages of easy availability of the cyclization precursors, operational simplicity,

The properties of isomeric azulene derivatives, substituted through the 5-membered ring, were examined using a combination of experimentation and theoretical calculations for a series of well-defined electroactive oligomers.

A novel family of stimuli-responsible polyazulenes connected through the seven-membered ring, in contrast to traditional five-membered connectivity, have been prepared by Yamamoto-, Sonogashira-, and Stille-coupling of 4,7-dibromoazulenes. Polymer absorption can be tuned by structural modification of the conjugated backbones with UV-vis and EPR studies indicating that the seven-membered ring connection of the azulene unit is effective for the generation and stabilization of azulenium cations. Th

Treatment of arylacetylenes and cyanogen bromide in ClCH(2)CH(2)Cl with a catalytic amount of GaCl(3) afforded (Z)-β-bromoacrylonitriles with high regio- and stereoselectivity.

We disclose a series of silicon-bridged diazulenylmethyl cations as stable and one-dimensionally π-extended carbocations. Connecting nonbenzenoid azulenes to a carbocation center at an appropriate position while reinforcing a planar arrangement effectively delocalizes a positive charge over the π-conjugated skeleton. This structural constraint endows the carbocations with not only high chemical stability with the p<i>K</i>_R⁺ value of around 9.5, despite the absence of any e

Use of an iridium catalyst allowed the efficient dehydrogenative functionalization of C-H bonds of azulenes with the production of hydrogen as the sole byproduct. The reaction occurred with excellent chemo- and regioselectivities to provide 2-silylazulenes even without any directing groups. Effective conjugation through the 2-position of the azulene ring was demonstrated by the unique stimuli-responsiveness against an acid-base reaction.

An iridium-catalyzed regioselective sequential silylation and borylation of heteroarenes was developed, which represents a rare example of unsymmetrical intermolecular C-H bond difunctionalization through the introduction of two different functionalities during a one-pot transformation. Although the substrate scope for the dehydrogenative silylation of heteroarenes has been limited mainly to electron-rich five-membered rings, the current reaction proceeds with both electron-rich and electron-def

Use of a rhodium catalyst with (R)-(S)-BPPFA ligand allows efficient synthesis of sila[n]helicenes via dehydrogenative silylation of C-H bonds. By selecting the proper ligands, the current method provides the ability to prepare unsymmetrical sila[n]helicene derivatives without any oxidants. The resulting sila[6]helicene is a rare example of a five-membered ring-fused [6]helicene, which was isolated as a single pure enantiomer without substituents on the terminal benzene rings.

The combination of diiodomethylboronate ester, CrCl₂ with TMEDA promoted borylcyclopropanation of unactivated alkenes under mild conditions. Compared with the typical Simmons-Smith cyclopropanation, the current protocol offers the following advantages: (1) the reaction proceeds stereoselectively with disubstituted alkenes even without hydroxy or alkoxy groups; (2) both electron-rich and electron-deficient alkenes can be applicable; and (3) the reaction does not require potentially fla

Rhodium-catalyzed dehydrogenative germylation leading to unsymmetrically functionalized 9-germafluorenes via Ge-H and C-H bond activation is described. Despite the significant achievements made in dehydrogenative functionalization of C-H bonds, only a limited number of examples with the fourth-row atom-H bonds have been reported. The current method enabled the synthesis of various 9-germafluorene derivatives, including tetracyclic as well as donor-acceptor substituted germoles, which may be usef

Treatment of 2-(cyanomethyl)phenyl esters with a catalytic amount of Pd(OAc)(2), PCy(3), and Zn afforded 3-acyl-2-aminobenzofuran derivatives in good to excellent yields, which can be used as building blocks for the synthesis of benzofuran fused heterocycles.