Yoshihiko Yamamoto

Synthesis of 4-arylcoumarins via Cu-catalyzed hydroarylation with arylboronic acids.

In the presence of 2-4 mol % of CuOAc, methyl phenylpropiolates having a MOM-protected hydroxy group at the ortho position underwent hydroarylation with various arylboronic acids in MeOH at ambient temperature, resulting in the formation of 4-arylcoumarins in high yields after the acidic workup. This method was effectively used for the synthesis of biologically active natural and artificial compounds.

Synthesis of chromans via [3 + 3] cyclocoupling of phenols with allylic alcohols using a Mo/o-chloranil catalyst system.

The combination of a molybdenum complex (CpMoCl(CO)(3) or [CpMo(CO)(3)](2)) and o-chloranil was used as a catalyst in the [3 + 3] cyclocoupling of phenols and allylic alcohols under microwave heating conditions. Substituted chromans were selectively obtained in moderate to good isolated yields.

Synthesis of benzo-fused lactams and lactones via Ru(II)-catalyzed cycloaddition of amide- and ester-tethered α,ω-diynes with terminal alkynes: electronic directing effect of internal conjugated carbonyl group

In the presence of a catalytic amount of Cp*RuCl(cod), 1,6- and 1,7-diynes connected by an amide or an ester tether underwent cycloaddition with terminal alkynes at room temperature to give rise to cycloadducts in 40-93% yields with 63 : 37-83 : 17 regioisomer ratios.

Selective Synthesis of Fused Cyclooctatetraenes by [4+4] Coupling Between Two Different Diene Units

In the presence of CuCl and 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, the [4 + 4] coupling between zirconacyclopentadienes and 1,3-diiodobutadienes fused through an oxygen or nitrogen five-membered ring proceeded at ambient temperature to afford fully substituted polycyclic cyclo-octatetraenes in good yields. The fused ring moiety of the diiodides plays a critical role. The corresponding acyclic diiodide and a cyclohexane-fused analogue gave no coupling product, and a cyclopentane derivative showed only moderate reactivity. Correlation of the structures of the diiodides and their reactivity was established by an X-ray and density functional study.

Versatile Friedel–Crafts-Type Alkylation of Benzene Derivatives Using a Molybdenum Complex/ortho-Chloranil Catalytic System

A variety of molybdenum complexes catalyze Friedel-Crafts-type alkylation reactions of benzene derivatives with alkenes and alcohols in the presence of an organic oxidant, o-chloranil. The utilization of [Mo(CO)(6)] and two equivalents of o-chloranil catalytically furnished the hydroarylation product of norbornene with p-xylene at 80 degrees C, whereas [Cr(CO)(6)] and [W(CO)(6)] failed to catalyze the same reaction, thus indicating the importance of the molybdenum source. The best results were obtained when a molybdenum(II) complex [CpMoCl(CO)(3)] (Cp=cyclopentadienyl) was used as a precatalyst. The hydroarylation reactions also took place with styrenes, cyclohexenes, and 1-hexene as olefin substrates. The electrophilic-substitution mechanism was proposed on the basis of the ortho/para selectivities and the Markovnikov selectivities observed for the hydroarylation products. Our hypothesis was further corroborated by the fact that in the presence of the [CpMoCl(CO)(3)]/o-chloranil catalytic system, secondary, benzylic, or allylic alcohols participated in the alkylation of benzenes with similar selectivities.

Ruthenium-Catalyzed Transfer Oxygenative Cyclization of α,ω- Diynes: Unprecedented (2 + 2 + 1) Route to Bicyclic Furans via Ruthenacyclopentatriene

A novel oxygen-atom-transfer process enables the catalytic [2 + 2 + 1] synthesis of bicyclic furans from α,ω-diynes with DMSO. [CpRu(AN)(3)]PF(6) catalyzed the transfer oxygenative cyclization of diynes with aryl terminal groups, while those of diynes with alkyl terminal groups were effectively promoted by the corresponding Cp* complex. A mechanism for bicyclic furan formation via a ruthenacyclopentatriene was proposed on the basis of both experimental and theoretical studies.

PD(0)-CATALYZED SELECTIVE 2 + 2 + 2 CYCLOADDITION OF DIMETHYL NONA-2,7-DIYNE-1,9-DIOATE DERIVATIVES WITH DIMETHYL ACETYLENEDICARBOXYLATE

Abstract In the presence of 2.5 mol % of Pd 2 (dba) 3 and 5 mol % of PPh 3 , nearly equimolar amounts of dimethyl nona-2,7-diyne-1,9-dioate derivatives and dimethyl acetylenedicarboxylate (DMAD) were reacted in toluene at 110 °C to give indan, phthalin, and isoindoline derivatives selectively in moderate to good yields. The competing homo-couplings of both the diynediesters and DMAD were completely suppressed. The ester groups on the alkyne terminus plays an important role; the corresponding diynediketone and diynemonoester gave unsatisfactory results. The present Pd(0)-catalyzed cyclotrimerization was further extended to the intramolecular [2 + 2 + 2] cycloaddition of a triynediester.

Ru(ii)-catalyzed [2 + 2 + 2] cycloaddition of 1,2-bis(propiolyl)benzenes with monoalkynes leading to substituted anthraquinonesElectronic supplementary information (ESI) available: experimental procedures and analytical data. See http://www.rsc.org/suppdata/cc/b3/b301762a/

[2 + 2 + 2] cycloadditions of 1,2-bis(propiolyl)benzenes with monoalkynes were effectively catalysed by Cp*RuCl(cod) under mild conditions to give substituted anthraquinones in moderate to high yields.

A combined experimental and computational study on the cycloisomerization of 2-ethynylbiaryls catalyzed by dicationic arene ruthenium complexes.

Ruthenium-catalyzed cycloisomerization of 2-ethynylbiaryls was investigated to identify an optimal ruthenium catalyst system. A combination of [η(6) -(p-cymene)RuCl2 (PR3 )] and two equivalents of AgPF6 effectively converted 2-ethynylbiphenyls into phenanthrenes in chlorobenzene at 120 °C over 20 h. Moreover, 2-ethynylheterobiaryls were found to be favorable substrates for this ruthenium catalysis, thus achieving the cycloisomerization of previously unused heterocyclic substrates. Moreover, several control experiments and DFT calculations of model complexes were performed to propose a plausible reaction mechanism.

Selective synthesis of C-arylglycosides via Cp*RuCl-catalyzed partially intramolecular cyclotrimerizations of C-alkynylglycosides.

In the presence of catalytic amounts of Cp*RuCl(cod), the partially intramolecular cyclotrimerizations of various C-alkynylglycosides and C-diynylglycosides proceeded at ambient temperature to afford C-arylglycosides.