Organocatalytic aldol addition reaction of cyclic hemiacetals to aldehydes

Regenerative γ-Lactone Annulations: A Modular, Iterative Approach to Oligo-tetrahydrofuran Molecular Stairs and Related Frameworks

“…Thus, triethylsilane-mediated reductive deoxygenation 14 It was of interest to explore whether appropriate substituents could be installed at the ring junction on the oligo-THFs to generate interesting new functionality on this scaffold. For this purpose, γ-butyrolactone 10 was subjected to allylation in the presence of excess allyl bromide at a slightly elevated temperature to furnish geminally diallylated product 27 as an exclusive product (Scheme 5).…”

“…At this point it was considered appropriate to demonstrate that parent, unsubstituted polycyclic oligo-THFs could also be readily prepared following a minor deviation at step 3 of the strategy outlined above. Thus, triethylsilane-mediated reductive deoxygenation 14 of the intermediate lactols 23 and 25 en route from 18 and 20 delivered 24 and 26 respectively (Scheme 4).…”

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.…”