Alder Reaction Of Aldehydes Research Articles

Organocatalytic oxa-Diels–Alder reaction of α,β-unsaturated ketones under non-classical conditions

Non-classical activation techniques improve the organocatalysed oxa-Diels–Alder reaction of aldehydes with enones.

ChemInform Abstract: An Efficient Domino Reaction in Ionic Liquid: Synthesis and Biological Evaluation of Some Pyrano‐ and Thiopyrano‐Fused Heterocycles.

AbstractA series of pyrazolopyran annulated‐pyrano‐fused coumarins (V) and thiopyrano‐fused quinolones (III) are obtained in an improved domino/Knoevenagel‐hetero‐Diels—Alder reaction of aldehydes (I) and (IV) with pyrazolones (II).

ChemInform Abstract: Organocatalytic Enantioselective Hetero‐Diels—Alder Reaction of Aldehydes and o‐Benzoquinone Diimide: Synthesis of Optically Active Hydroquinoxalines.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

DIANANE‐CrIII‐salen Complexes as Highly Enantioselective Catalysts for Hetero‐Diels–Alder Reactions of Aldehydes with Dienes

AbstractA new type of chromium‐salen complex bearing DIANANE (endo,endo‐2,5‐diaminonorbornane) as chiral backbone has been synthesized and applied to the hetero‐Diels–Alder reaction of Danishefsky’s diene with various aldehydes. The reactions afford the corresponding 2‐substituted 2,3‐dihydro‐4H‐pyran‐4‐ones in high yields and enantioselectivities (up to 96 % ee). The effect of different counteranions of the complex on reactivity as well as enantioselectivity has been investigated. Besides Danishefsky’s diene, reaction of the less reactive 1‐methoxybutadiene with benzaldehyde and ethyl glyoxylate can be effected by the chromium catalysts as well.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Assembled Dendritic Titanium Catalysts for Enantioselective Hetero‐Diels—Alder Reaction of Aldehydes with Danishefsky′s Diene.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Assembled dendritic titanium catalysts for enantioselective hetero-Diels-Alder reaction of aldehydes with Danishefsky's diene.

A new type of dendritic 2-amino-2'-hydroxy-1,1'-binaphthyl (NOBIN)-derived Schiff-base ligands have been synthesized and applied to the titanium-catalyzed hetero-Diels-Alder reaction of Danishefsky's diene with aldehydes. These reactions afforded the corresponding 2-substituted 2,3-dihydro-4H-pyran-4-ones in quantitative yields and with excellent enantioselectivities (up to 97.2 % ee). The disposition of the dendritic wedges and the dendron size in the ligands were found to have significant impact on the enantioselectivity of the reaction. The recovered dendritic catalyst could be reused without further addition of the Ti source or a carboxylic acid additive for at least three cycles, retaining similar activity and enantioselectivity. The high stability of this type of assembled dendritic titanium catalyst may be attributed to the stabilization effect of large-sized dendron units in the catalyst molecule. The other important phenomenon observed with this catalyst system is that a higher degree of asymmetric amplification has been achieved by attachment of the dendron unit to the chiral ligand, which represents a new advantage of dendrimer catalysts for asymmetric reactions using chiral ligands of lower optical purity.

Chiral Hetero Diels—Alder Products by Enantioselective and Diastereoselective Zirconium Catalysis. Scope, Limitation, Mechanism, and Application to the Concise Synthesis of (+)-Prelactone C and (+)-9-Deoxygoniopypyrone.

Catalytic asymmetric hetero Diels−Alder (HDA) reactions using a chiral zirconium complex have been developed. The reactions of aldehydes with Danishefsky's dienes proceeded smoothly to afford the corresponding pyranone derivatives in high yields with high diastereo- and enantioselectivities in the presence of a chiral zirconium complex, which was prepared from zirconium tert-butoxide, (R)-3,3‘-diiodobinaphthol or its derivative, a primary alcohol, and a small amount of water. It is noted that 2,3-trans-pyranone derivatives were obtained with remarkably high diastereo- and enantioselectivities in the reaction with 4-methyl Danishefsky's diene. This is the first example of catalytic asymmetric trans-selective hetero Diels−Alder reactions of aldehydes. Furthermore, asymmetric HDA reactions with 4-benzyloxy Danishefsky's dienes were conducted to afford 2,3-cis-pyranone derivatives in high selectivities. Isolation of an intermediate of this asymmetric hetero Diels−Alder reaction indicated that the reaction pro...

ChemInform Abstract: A Highly Enantioselective Hetero‐Diels—Alder Reaction of Aldehydes with Danishefsky′s Diene Catalyzed by Chiral Titanium(IV) 5,5′,6,6′,7,7′,8,8′‐Octahydro‐1,1′‐bi‐2‐naphthol Complexes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A highly enantioselective hetero-Diels-Alder reaction of aldehydes with Danishefsky's diene catalyzed by chiral titanium(IV) 5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphthol complexes.

The catalytic effect of chiral Lewis acids on the hetero-Diels-Alder reaction between aldehydes and Danishefsky's diene (1) has been investigated. A variety of combinations of different ligands and Lewis acids have been examined as catalysts for the hetero-Diels-Alder reaction between benzaldehyde and 1, and it has been found that the readily accessible Ti(IV)-H(8)-BINOL (TiHBOL) complex is a very effective catalyst for the reaction, leading to products with very high enantioselectivity (up to 99% ee) and yield (92%). The hetero-Diels-Alder reaction of other aldehydes with 1 under the catalysis of TiHBOL is a general reaction which proceeds well with very high enantioselectivity and isolated yield for various aldehydes at 0 degrees C to room temperature. Based on the experimental results, the proposed mechanism of the hetero-Diels-Alder reaction and the dihedral angle effects of ligands are discussed.