The development of a new class of hydrazide type organocatalyst, (4R,5R)-1,3-bis(isopropylamino)-4,5-dihenylimidazolidin-2-one 2a, for enantioselective DielsâAlder reactions between cyclopentadiene and α,β-unsaturated aldehydes are presented. The new organocatalyst 2a promoted the reaction, affording DielsâAlder adducts in good yields with good levels of enantioselectivity.
The development of highly active acyclic chiral hydrazides for asymmetric iminium ion organocatalysis
作者:Eoin Gould、Tomas Lebl、Alexandra M. Z. Slawin、Mark Reid、Tony Davies、Andrew D. Smith
DOI:10.1039/c3ob41719k
日期:——
Double asymmetric induction has been employed as a tool to optimise pyrazolidinone-derived organocatalysts for the asymmetric iminiumion catalysed Diels–Alder reaction. Mechanistic studies revealed a superior hydrazide catalyst deriving from methanolysis of the chiral pyrazolidinone precursor. This catalyst displays unusually high endo diastereoselectivity and good enantioselectivity with a range
Caveat in the stereochemical outcome of the organocatalytic Diels–Alder reaction in PEG-400
作者:Pantapalli M. Anitha、Prathama S. Mainkar、Shivakrishna Kallepu、V. S. Phani Babu、Cirandur Suresh Reddy、Srivari Chandrasekhar
DOI:10.1039/c6ra15035g
日期:——
The organocatalyticDiels–Alderreaction in non-conventional solvent (PEG-400) has yielded cycloaddition products with diastereoselectivities hitherto not reported in detail using classical reaction conditions.
Camphor Sulfonyl Hydrazines (CaSH) as Organocatalysts in Enantioselective Diels−Alder Reactions
作者:Hao He、Bao-Jian Pei、Ho-Hsuan Chou、Tian Tian、Wing-Hong Chan、Albert W. M. Lee
DOI:10.1021/ol8005826
日期:2008.6.1
Cyclic sulfonyl hydrazine was demonstrated for the first time as a new functionality for organocatalysis. A series of six-membered cyclic hydrazines derived from camphor sulfonic acid were synthesized. With trichloroacetic acid as cocatalyst, they are efficient organocatalysts for enantioselectiveDiels-Alderreactions with good chemical yields and up to 96% ee. The reactions took place in brine at
Highly active asymmetric Diels–Alder reactions catalyzed by C2-symmetric bipyrrolidines: catalyst recycling in water medium and insight into the catalytic mode
designed and synthesized for asymmetric organocatalytic Diels–Alder reactions of α,β-unsaturatedaldehydes. The remarkable rate-accelerating effect for the cycloaddition reaction has been observed in aqueous medium. The catalyst 1c·2HClO4 can be recovered and reused several times by simple extraction without significant loss of catalytic activity and stereoselectivity. The catalytic mode has been demonstrated