Kiyomi Kakiuchi

Rh(I)-catalyzed CO gas-free carbonylative cyclization reactions of alkynes with 2-bromophenylboronic acids using formaldehyde.

The rhodium(I)-catalyzed reaction of alkynes with 2-bromophenylboronic acids in the presence of paraformaldehyde resulted in a CO gas-free carbonylative cyclization, yielding indenone derivatives. [RhCl(BINAP)](2) and [RhCl(cod)](2) were responsible for the decarbonylation of formaldehyde and the subsequent carbonylation of alkynes with 2-haloboronic acids, respectively, leading to efficient whole carbonylation. Sterically bulky and electron-withdrawing groups on unsymmetrically substituted alkynes favored the alpha-position of indenones.

Synthesis, Structure and Reactivities of [6]Paracyclophanes.

Abstract The synthesis, structure and reactivities of [6]paracycophanes 2a-c, the smallest bridged [n]paracydophanes so far isolated, are described. The parent hydrocarbon 2a has been efficiently synthesized by oxidative decarboxylation of [6.2-2]propellenecarboxylic acid (7) by lead tetraacetate. The 8-carbomethoxy derivative 2b has been quantitatively synthesized by thermal valence isomerization of the [6.2.2]propelladiene (4b) (Dewar isomer of 2b). X-Ray structure analysis of the crystalline 2c has revealed that the benzene ring of 2c severely deformed into a boat conformation with deformation angles of α= 20.5° and β = 18.5°. Furthermore, the bond angles of the bridging chain (C(2), C(3), C(4) and C(5)) are considerably expanded from the normal sp3 angle. Vaporphase thermolysis of 2a gives the spiro triene 12 via homolysis at the benzyl position. Add-catalyzed isomerization of 2a with trifluoroacetic add takes place readily to afford the meta and ortho isomers 13a and 14a in a ratio of 1:3. UV irradiation of the ester 2b brings about valence isomerization to the Dewar isomer 4b which isomerizes slowly to the prismane derivative 15a on further irradiation. A [4+2] cycloaddition of 2a with N-phenyl-l,2,4-triazoline-3,5-dione occurs at room temperature to give mainly adduct 16. Addition of bromine to 2a takes place to furnish quantitatively the unstable 1,4-addition product 18. Oxidation of 2a with mCPBA readily takes place to give the dienone dimer 20 which affords on UV irradiation the cage diketone 21 derived from intramolecular photocycloaddition.

Regioselective Rapid Synthesis of Fully Substituted 1,2,3-Triazoles Mediated by Propargyl Cations

Regioselective rapid triazole syntheses at low temperature are described. Organic azides and propargyl cations generated by acids gave fully substituted 1H-1,2,3-triazoles. Most reactions could be performed in 5 min at not only rt but also -90 °C. Both terminal and internal alkynes were acceptable, and the sterically bulky substituents could afford the products smoothly. Various types of three-component coupling reactions were demonstrated, and the presence of allenylaminodiazonium intermediates was indicated.

Rh(I)-catalyzed asymmetric synthesis of 3-substituted isoindolinones through CO gas-free aminocarbonylation.

A highly efficient and accessible synthesis of chiral 3-substituted isoindolinone frameworks is described. The synthesis involved the Rh(I)-catalyzed asymmetric arylation of boronic acids to 2-halobenzaldimines and the subsequent Rh(I)-catalyzed intramolecular aminocarbonylation of the resulting 2-halobenzylamines using an aldehyde as the carbonyl source. The method tolerates a variety of functional groups, yielding isoindolinone derivatives in moderate to high yields with high ee-values. In addition, two Rh(I)-catalyzed transformations could be efficiently accomplished in a one-pot sequence to give chiral isoindolinones by the simple addition of a ligand and an aldehyde after the Rh(I)-catalyzed asymmetric arylation.

Image sensor pixel with on-chip high extinction ratio polarizer based on 65-nm standard CMOS technology

In this study, we demonstrate a polarization sensitive pixel for a complementary metal-oxide-semiconductor (CMOS) image sensor based on 65-nm standard CMOS technology. Using such a deep-submicron CMOS technology, it is possible to design fine metal patterns smaller than the wavelengths of visible light by using a metal wire layer. We designed and fabricated a metal wire grid polarizer on a 20 × 20 μm(2) pixel for image sensor. An extinction ratio of 19.7 dB was observed at a wavelength 750 nm.

Efficient Synthesis of α,β-Unsaturated Alkylimines Performed with Allyl Cations and Azides: Application to the Synthesis of an Ant Venom Alkaloid

An efficient synthesis of α,β-unsaturated alkylimines at low temperature using azides has been developed. Carbocations generated from allyl alcohols helped achieve a rapid conversion under mild conditions with azides to afford reactive α,β-unsaturated imines. Hydroxy or alkoxy groups are essential for these transformations, and utilizing readily accessible allyl alcohols gave a wide extension of substrates. The efficiency of this novel method is demonstrated in the total synthesis of an iminium ant venom alkaloid.

A new route for the construction of the AB-ring core of Taxol

Abstract A new method for the construction of the AB-ring core of Taxol was developed utilizing a new skeletal transformation protocol as a pivotal step. The acid-catalyzed rearrangement of the cyclopentenone–allene photoadduct gave a bridged seven-membered ketone, which was easily transformed, using the intramolecular Suzuki reaction and the oxidative cleavage of the vicinal diol, to the bicyclic diketone.

Cross-coupling reactions proceeding through η1- and η3-propargyl/allenyl–palladium(II) intermediates

Abstract The efficiency of cross-coupling between propargyl electrophiles and organotin(IV) or zinc(II) compounds catalyzed by phosphine–palladium complexes has been examined as a function of PR3/Pd ratio, the nature of the organometallics, and the nature of the leaving group of the electrophile. The coupling between RCCCH2Cl and PhSnBu3 proceeded much more smoothly by use of a catalyst precursor having a PPh3/Pd ratio of 1/1 rather than 4/1, while the rate of the coupling using PhCCSnBu3, instead of PhSnBu3, was less sensitive to the PPh3/Pd ratio. The regiochemistry of the coupling (formation of alkyne or allene) was also sensitive to the PPh3/Pd ratio in the case of the reaction between RCCCH2Cl and PhZnCl, but was much less sensitive in the reaction using PhSnBu3. These results have been rationalized by a general mechanistic scheme involving not only η1-propargyl or η1-allenylpalladium(II) which was considered in previous studies but also η3-propargylpalladium(II) species as a new reactive intermediate candidate. The carbonates, RCCCH2OCOC2H5, failed to undergo as clean a cross-coupling as was found with the chlorides, but instead provided products arising from the coupling of two RCCCH2 units without any participation of organotin(IV) reagents.

Utilization of Aldoses as a Carbonyl Source in Cyclocarbonylation of Enynes

The reaction of enynes with acetyl-masked aldoses in the presence of a rhodium(I) catalyst resulted in cyclocarbonylation, thus avoiding the direct use of carbon monoxide, to afford bicyclic cyclopentenones. In rhodium catalysis, aldoses serve as a carbon monoxide equivalent by donating their carbonyl moieties on the acyclic aldehyde form to enynes. A variety of aldoses, including D-glucose, D-mannose, D-galactose, D-xylose, and D-ribose, can be used as a carbonyl source. Using the method, a wide variety of enynes were cyclocarbonylated in 22-67% yields. An asymmetric variant also proceeded with moderate to high enantioselectivity.

Stereocontrolled total synthesis of (±)-isocomene and (±)-β-isocomene via ring enlargement

A total synthesis of (±)-isocomene(1) and (±)-β-isocomene (2) employing a chelation-controlled regioselective epoxide–carbonyl rearrangement as the key step has been realized.