Kazuaki Ishihara

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXT3,4,5-Trifluorobenzeneboronic Acid as an Extremely Active Amidation CatalystKazuaki Ishihara, Suguru Ohara, and Hisashi YamamotoView Author Information Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-01, Japan Cite this: J. Org. Chem. 1996, 61, 13, 4196–4197Publication Date (Web):June 26, 1996Publication History Received16 April 1996Published online26 June 1996Published inissue 1 January 1996https://pubs.acs.org/d

Scandium trifluoromethanesulfonate (triflate), which is commercially available, is a practical and useful Lewis acid catalyst for acylation of alcohols with acid anhydrides or the esterification of alcohols by carboxylic acids in the presence of p-nitrobenzoic anhydrides. The remarkably high catalytic activity of scandium triflate can be used for assisting the acylation by acid anhydrides of not only primary alcohols but also sterically-hindered secondary or tertiary alcohols. The method present

In order to promote atom efficiency in synthesis and to avoid the generation of environmental waste, the use of stoichiometric amounts of condensing reagents or excess substrates should be avoided. In esterification, excesses of either carboxylic acids or alcohols are normally needed. We show that the direct condensation of equimolar amounts of carboxylic acids and alcohols can be achieved with the use of hafnium(IV) salts, such as commercially available hafnium(IV) chloride and hafnium(IV) tert

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTScandium Trifluoromethanesulfonate as an Extremely Active Acylation CatalystKazuaki Ishihara, Manabu Kubota, Hideki Kurihara, and Hisashi YamamotoCite this: J. Am. Chem. Soc. 1995, 117, 15, 4413–4414Publication Date (Print):April 1, 1995Publication History Published online1 May 2002Published inissue 1 April 1995https://pubs.acs.org/doi/10.1021/ja00120a030https://doi.org/10.1021/ja00120a030research-articleACS PublicationsRequest reuse permissionsArticle

Both catalysts work: A highly enantioselective direct Mannich-type reaction of N-Boc-protected aldimines with 1,3-dicarbonyl compounds has been developed with the use of a chiral phosphoric acid in the presence or absence of CaII. The absolute stereoselectivity of the phosphoric acid catalysis was found to be opposite to that of the calcium phosphate catalysis (see scheme; Boc=tert-butoxycarbonyl).

We have realized the first enantioselective organocatalytic Diels-Alder reaction between alpha-substituted acroleins, such as alpha-acyloxyacroleins, and not only cyclic but also acyclic dienes. alpha-Acyloxyacroleins are useful as synthetic equivalents of alpha-haloacroleins. The present catalyst could be prepared in situ from pentafluorobenzenesulfonic acid (2.5-3.0 equiv) and chiral triamine (1 equiv) derived from H-l-Phe-l-Leu-N(CH2CH2)2. The enantioselective Diels-Alder reaction of 5-(benzy

Arylboron compounds, ArnB(OH)3–n (n = 1–3), bearing electron-withdrawing aromatic groups such as triarylboranes, diarylborinic acids, and arylboronic acids represent a new class of air-stable and water-tolerant Lewis acid or Brønsted acid catalysts in organic synthesis. In particular, while tris(pentafluorophenyl)borane has primarily been used as a co-catalyst in metallocene-mediated olefin polymerization, its potential as a Lewis acid catalyst for organic transformation is now much more extensi

An economical and environmentally benign process for the preparation of nitriles by the dehydration of primary amides and aldoximes is catalyzed by rhenium(VII) oxo complexes such as perrhenic acid and trimethylsilylperrhenate (see scheme). The reaction proceeds at azeotropic reflux (with the removal of water) under essentially neutral conditions.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA New Chiral BLA Promoter for Asymmetric Aza Diels-Alder and Aldol-Type Reactions of IminesKazuaki Ishihara, Mayumi Miyata, Kouji Hattori, Toshiji Tada, and Hisashi YamamotoCite this: J. Am. Chem. Soc. 1994, 116, 23, 10520–10524Publication Date (Print):November 1, 1994Publication History Published online1 May 2002Published inissue 1 November 1994https://pubs.acs.org/doi/10.1021/ja00102a019https://doi.org/10.1021/ja00102a019research-articleACS Publicati

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn extremely simple, convenient, and selective method for acetylating primary alcohols in the presence of secondary alcoholsKazuaki Ishihara, Hideki Kurihara, and Hisashi YamamotoCite this: J. Org. Chem. 1993, 58, 15, 3791–3793Publication Date (Print):July 1, 1993Publication History Published online1 May 2002Published inissue 1 July 1993https://pubs.acs.org/doi/10.1021/jo00067a005https://doi.org/10.1021/jo00067a005research-articleACS PublicationsReques

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBronsted Acid Assisted Chiral Lewis Acid (BLA) Catalyst for Asymmetric Diels-Alder ReactionKazuaki Ishihara and Hisashi YamamotoCite this: J. Am. Chem. Soc. 1994, 116, 4, 1561–1562Publication Date (Print):February 1, 1994Publication History Published online1 May 2002Published inissue 1 February 1994https://pubs.acs.org/doi/10.1021/ja00083a048https://doi.org/10.1021/ja00083a048research-articleACS PublicationsRequest reuse permissionsArticle Views2446Alt

Brønsted acid-assisted chiral Lewis acid (BLA) was highly effective as a chiral catalyst for the enantioselective Diels−Alder reaction of both α-substituted and α-unsubstituted α,β-enals with various dienes. Hydroxy groups in optically active binaphthol derivatives and boron reagents with electron-withdrawing substituents were used as Brønsted acids and Lewis acids, respectively. Intramolecular Brønsted acids in a chiral BLA catalyst played an important role in accelerating the rate of Diels−Ald