Chiral phosphine-squaramides as enantioselective catalysts for the intramolecular Morita–Baylis–Hillman reaction
作者:Hong-Liang Song、Kui Yuan、Xin-Yan Wu
DOI:10.1039/c0cc03187a
日期:——
squaramides containing tertiary phosphine were developed as chiral bifunctional organic catalysts to promote the asymmetric intramolecularMorita-Baylis-Hillmanreaction of omega-formyl-enones. The adducts were obtained in high yields with good-to-excellent enantioselectivity (up to 93% ee).
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
available hydroxamic acids were leveraged to access challenging nitrones in the presence of H3PO4 as a Brønsted acid catalyst and engaged in an intramolecular (3+2) annulation reaction to make valuable cyclopentane-fused isoxazolidines with high yields and excellent diastereoselectivity. The products were further utilized in a unique base-promoted benzilic amide rearrangement to provide cyclopentane-fused
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。
Highly Enantioselective Intramolecular Morita-Baylis-Hillman Reaction Catalyzed by Mannose-Based Thiourea-phosphine
AbstractThe saccharide‐based chiral bifunctional thiourea‐phosphines were developed as chiral organocatalysts for the intramolecular Morita‐Baylis‐Hillman reaction of ω‐formyl‐enones. With only 2 mol% of thiourea‐phosphine catalyst 3c, chiral functionalized cyclohexenes were achieved under mild reaction conditions with excellent yields and enantioselectivities.