pharmaceutical drug synthesis. We herein report a mild pathway for the efficient enantioselective synthesis of these compounds directly from aldehydes through synergistic cooperation between a neutral eosin Y hydrogen atom transfer photocatalyst and a chiral rhodium Lewisacid catalyst. This method is distinguished by its operational simplicity, abundant feedstocks, atom economy, and ability to generate products
the presence of acetic anhydride in THF produces the corresponding enol lactones in high enantioselectivities through enantioselectiveMichaeladditionsfollowed by cyclization with removal of the pyrazole auxiliary. Other related nucleophile precursors can be successfully applied in the enantioselective enol lactonesynthesis under the double catalytic conditions.
Organocatalysis in Conjugate Amine Additions. Synthesis of β-Amino Acid Derivatives
作者:Mukund P. Sibi、Kennosuke Itoh
DOI:10.1021/ja071739c
日期:2007.7.1
Conjugateaddition of O-protected hydroxylamines to pyrazole-derived enoates proceeds with high efficiency and enantioselectivity when chiral thioureas are used as activators. A wide variety of substrates undergo conjugate amine addition providing access to enantioenriched β-aminoacidderivatives. Structural requirements for the optimal thiourea catalyst have been established, and the results suggest
Enantioselective Conjugate Addition of Hydrazines to α,β-Unsaturated Imides. Synthesis of Chiral Pyrazolidinones
作者:Mukund P. Sibi、Takahiro Soeta
DOI:10.1021/ja069312d
日期:2007.4.1
This manuscript describes a highlyenantioselectiveconjugate hydrazine addition to α,β-unsaturatedimides. The achiral template used has a significant impact on product enantioselectivity. Reactions at lower temperatures provide a protocol to add substituted hydrazines with selectivity resulting in the formation of a single pyrazolidinone product (>98:2 selectivity). A variety of chiral pyrazolidinones
Design of a Small-Molecule Catalyst Using Intramolecular Cation−π Interactions for Enantioselective Diels−Alder and Mukaiyama−Michael Reactions: <scp>l</scp>-DOPA-Derived Monopeptide·Cu(II) Complex
作者:Kazuaki Ishihara、Makoto Fushimi
DOI:10.1021/ol060651l
日期:2006.4.1
[reaction: see text] We have designed a small-molecule artificial metalloenzyme that is prepared in situ from Cu(OTf)(2) or Cu(NTf(2))(2) (1.0 equiv) and l-DOPA-derived monopeptide (1.1 equiv). This catalyst (2-10 mol %) is highly effective for the enantioselectiveDiels-Alder (DA) and Mukaiyama-Michael (MM) reactions with alpha,beta-unsaturated 1-acyl-3,5-dimethylpyrazoles. The present results demonstrate