Stereodivergent Organocatalytic Intramolecular Michael Addition/Lactonization for the Asymmetric Synthesis of Substituted Dihydrobenzofurans and Tetrahydrofurans
نویسندگان
چکیده
A stereodivergent asymmetric Lewis base catalyzed Michael addition/lactonization of enone acids into substituted dihydrobenzofuran and tetrahydrofuran derivatives is reported. Commercially available (S)-(-)-tetramisole hydrochloride gives products with high syn diastereoselectivity in excellent enantioselectivity (up to 99:1 d.r.syn/anti , 99 % eesyn ), whereas using a cinchona alkaloid derived catalyst gives the corresponding anti-diastereoisomers as the major product (up to 10:90 d.r.syn/anti , 99 % eeanti ).
منابع مشابه
Observation of neighboring ortho-hydroxyl group participation in organocatalytic asymmetric sequential Michael-lactonization reactions: synthesis of highly substituted chiral spirodihydrocoumarins.
A general approach to asymmetric synthesis of highly substituted spirodihydrocoumarins with a quaternary stereocenter was achieved through neighboring ortho-hydroxyl group induced sequential Michael-lactonization reactions on 2-(2-nitrovinyl)phenols with alkyl cyclopentanone-2-carboxylates in the presence of a catalytic amount of quinine-NH-thiourea followed by p-TSA.
متن کاملOrganocatalytic enantioselective Michael addition of cyclic hemiacetals to nitroolefins: a facile access to chiral substituted 5- and 6-membered cyclic ethers.
An efficient aminocatalytic enantioselective Michael addition of readily available cyclic hemiacetals to nitroolefins has been developed. The strategy serves as a powerful approach to synthetically valuable chiral 3-substituted tetrahydrofurans (THFs) and tetrahydropyrans (THPs). The synthetic utilities of the versatile Michael adducts also have been demonstrated in the synthesis of 2,3-disubst...
متن کاملOrganocatalytic synthesis of polysubstituted tetrahydrofurans from alkenes†
A novel, organocatalytic and environmentally friendly protocol for the synthesis of polysubstituted tetrahydrofurans from trivial starting materials has been described. By employing 2,2,2-trifluoroacetophenone-mediated oxidation, which utilizes H2O2 as a green oxidant, we introduce a sustainable procedure that embraces the principles of green chemistry for the production of substituted tetrahyd...
متن کاملCalcium Chloride catalyzed Intramolecular Oxa Michael addition of 2’-Hydroxychalcone to Flavanone
An efficient cyclization of 2’-hydroxychalcone to flavanone using calcium chloride as a catalyst was developed. The scope of the reaction was studied with substituted 2’-hydroxychalcone and these chalcones was converted into corresponding flavanone in good yield. The merits of this method are inexpensive and easily available catalyst, easy workup procedure, avoid use of toxic solvent
متن کاملCalcium Chloride catalyzed Intramolecular Oxa Michael addition of 2’-Hydroxychalcone to Flavanone
An efficient cyclization of 2’-hydroxychalcone to flavanone using calcium chloride as a catalyst was developed. The scope of the reaction was studied with substituted 2’-hydroxychalcone and these chalcones was converted into corresponding flavanone in good yield. The merits of this method are inexpensive and easily available catalyst, easy workup procedure, avoid use of toxic solvent.
متن کامل