在 H 3 PO 4作为布朗斯台德酸催化剂存在下,利用容易获得的异羟肟酸来获得具有挑战性的硝酮,并进行分子内 (3+2) 成环反应,以高产率和优异的非对映选择性制备有价值的环戊烷稠合异恶唑烷。该产品进一步用于独特的碱促进的二苯乙醇酰胺重排,以提供带有三个连续立体中心的环戊烷稠合γ-内酰胺作为单一非对映体。
A series of chiral bifunctional phosphinothioureas derived from l-amino acids have been developed to promote the enantioselectiveintramolecularMorita–Baylis–Hillmanreaction. The process afforded the cyclic hydroxyl enones with up to 84% ee and good yields under mild conditions.
Chiral cyclohexane-based phosphinothioureas were found to be efficient organocatalysts for the enantioselective intramolecular Morita–Baylis–Hillmanreaction of ω-formyl-enone. Among the solvents screened, t-BuOH was the best one which provided good yield and enantioselectivity. Moreover in the presence of 3 mol % of phosphinothiourea 2b, the desired products were obtained in good-to-excellent yields
Chiral thiourea derivatives as organocatalyts in the enantioselective Morita-Baylis-Hillman reactions
作者:A. Ebru Aydin
DOI:10.24820/ark.5550190.p011.072
日期:——
Novel chiral bifunctional thiourea derivatives have been synthesised and successfully applied to the intermolecular Morita-Baylis-Hillman (MBH) reaction of an aromatic aldehyde with methyl vinyl ketone (MVK) and to the intramolecular MBH reaction of omega-formyl-enone. The corresponding products were obtained with high enantioselectivities (up to 98 % ee). The thiourea organocatalyst derived from a B-amino alcohol gave high enantioselectivities (92 % ee) in the intermolecular MBH reaction, whereas the same chiral ligand afforded the corresponding product in high yield (85 %) with moderate enantioselectivity (75 % ee) in the intramolecular MBH reaction. The use of a thiophene ring-containing thiourea derivative gave high enantioselectivities in the intermolecular and intramolecular MBH reactions (85 % and 95 % ee, respectively).[GRAPHICS].
Umpolung Reactivity of in Situ Derived Aryl Hydrazones: An Asymmetric Brønsted Acid Catalyzed Strategy to Access Fused Pyrazolidines