Substrate-Controlled, One-Pot Synthesis: Access to Chiral Chroman-2-one and Polycyclic Derivatives

Abstract

Based on the appropriate choice of electrophiles, one-pot, multicomponent, enantioselective domino reactions have been realized which contain a five-step sequence and provide highly efficient access to potentially bioactive chroman-2-one derivatives as a single diastereoisomer with excellent enantioselectivities and in high yields. This new strategy could significantly improve the previous protocol by directly starting from commercial 2-hydroxybenzaldehydes rather than preformed lactols, which have to be synthesized in several additional steps.

Strategies and Methods for the Catalytic Asymmetric Synthesis of Benzofuran/Benzopyran Fused Acetals: A Review

“…In 2016, Liu et al described a cascade catalysis process for the asymmetric sequential iminium-reduction/Michael addition/lactolization/cyclization reaction that permits the efficient formation of fused heterocycle derivatives 50 with consecutive chiral stereo- centers in good yields, excellent diastereoselectivities, and high enantioselectivities (Scheme 24, up to 6:1 dr and > 99% ee). [44] Soon later, the same group developed a similar asymmetric organocatalytic cascade process in the course of one operation to form the same structure as a single diastereoisomer, which produce water as the only stoichiometric byproduct (Scheme 25). [45] Later in 2021, they disclosed the cascade process consists of [4 + 2] cycloaddition, acetalization and hemiacetalization for the synthesis of chiral benzopyran-fused polycyclic acetals 54.…”

Organocatalytic, Asymmetric [2+2+2] Annulation to Construct Six-Membered Spirocyclic Oxindoles with Six Continuous Stereogenic Centers

“…Very recently, we and others independently reported research on the application of lactols or cyclic hemiaminals as nucleophiles under enamine activation to produce chiral substituted lactones, lactams, Very recently, we and others independently reported research on the application of lactols or cyclic hemiaminals as nucleophiles under enamine activation to produce chiral substituted lactones, lactams, and other interesting heterocycles with excellent enantioselectivity and diastereoselectivity [41][42][43][44][45][46]. In an effort to expand our exploration on the application of lactols or cyclic hemiaminals, herein we would like to report an asymmetric [2+2+2] annulation under an organo/organo dual catalytic system to produce six-membered carbocycles with six continuous stereogenic centers including an all-carbon quaternary center and spirooxindole moiety in the product structure.…”