9 research outputs found
Highly Enantioselective Synthesis of 2,3-Dihydroquinazolinones through Intramolecular Amidation of Imines
Enantioselective synthesis of 2,3-dihydroquinazolinones (DHQZs) was accomplished using readily available Sc(III)-<i>inda</i>-pybox as the catalyst. This is the first report on the metal catalyzed asymmetric intramolecular amidation of imines to synthesize DHQZs
Stereodivergent Synthesis of 3‑Aminooxindole Derivatives Containing Vicinal Tetrasubstituted Stereocenters via the Mannich Reaction
A highly
enantioselective stereodivergent synthesis of 3-aminooxindole
derivatives was accomplished via asymmetric Mannich reaction between
2-substituted benzofuran-3-one and isatin-derived ketimines. Both <i>anti</i> and <i>syn</i>-selective chiral 3,3-disubstituted
amino oxindoles bearing two adjacent tetrasubstituted stereogenic
centers with high yield and excellent enantioselectivities were obtained
using readily available cinchona-alkaloid derived organocatalysts.
The control experiment revealed that oxygen atom present in the benzofuran
ring played an important role in switching diastereodivergence. The
obtained Mannich product was further transformed into a biologically
important 2,3-dihydrobenzofuran derivative having three contiguous
stereocenters with no loss of enantioselectivity
Enantioselective Synthesis of Dihydrospiro[indoline-3,4′-pyrano[2,3‑<i>c</i>]pyrazole] Derivatives via Michael/Hemiketalization Reaction
A new
bifunctional squaramide organocatalyst derived from l-proline
mediated the first enantioselective synthesis of dihydrospiroÂ[indoline-3,4′-pyranoÂ[2,3-<i>c</i>]Âpyrazole] derivatives in excellent enantioselectivity
by reacting pyrazolones with isatylidine β,γ-unsaturated
α-ketoester. This new catalyst outperformed widely used thioureas
and squaramides in inducing enantioselectivity
Stereodivergent Synthesis of 3‑Aminooxindole Derivatives Containing Vicinal Tetrasubstituted Stereocenters via the Mannich Reaction
A highly
enantioselective stereodivergent synthesis of 3-aminooxindole
derivatives was accomplished via asymmetric Mannich reaction between
2-substituted benzofuran-3-one and isatin-derived ketimines. Both <i>anti</i> and <i>syn</i>-selective chiral 3,3-disubstituted
amino oxindoles bearing two adjacent tetrasubstituted stereogenic
centers with high yield and excellent enantioselectivities were obtained
using readily available cinchona-alkaloid derived organocatalysts.
The control experiment revealed that oxygen atom present in the benzofuran
ring played an important role in switching diastereodivergence. The
obtained Mannich product was further transformed into a biologically
important 2,3-dihydrobenzofuran derivative having three contiguous
stereocenters with no loss of enantioselectivity
Stereodivergent Synthesis of 3‑Aminooxindole Derivatives Containing Vicinal Tetrasubstituted Stereocenters via the Mannich Reaction
A highly
enantioselective stereodivergent synthesis of 3-aminooxindole
derivatives was accomplished via asymmetric Mannich reaction between
2-substituted benzofuran-3-one and isatin-derived ketimines. Both <i>anti</i> and <i>syn</i>-selective chiral 3,3-disubstituted
amino oxindoles bearing two adjacent tetrasubstituted stereogenic
centers with high yield and excellent enantioselectivities were obtained
using readily available cinchona-alkaloid derived organocatalysts.
The control experiment revealed that oxygen atom present in the benzofuran
ring played an important role in switching diastereodivergence. The
obtained Mannich product was further transformed into a biologically
important 2,3-dihydrobenzofuran derivative having three contiguous
stereocenters with no loss of enantioselectivity
Highly Enantioselective Synthesis of 2,3-Dihydroquinazolinones through Intramolecular Amidation of Imines
Enantioselective synthesis of 2,3-dihydroquinazolinones (DHQZs) was accomplished using readily available Sc(III)-<i>inda</i>-pybox as the catalyst. This is the first report on the metal catalyzed asymmetric intramolecular amidation of imines to synthesize DHQZs
Diastereoselective Construction of Tetrahydro-Dispiro[indolinone-3,2′-pyran-5′,4″-pyrazolone] Scaffolds via an Oxa-Michael Cascade [4 + 2] Annulation Reaction
A straightforward metal-free oxa-Michael cascade [4 +
2] annulation
reaction was established between isatin-derived Morita–Baylis–Hillman
(Is-MBH) alcohols with alkylidene pyrazolones to access structural
diverse tetrahydro-dispiro[indolinone-3,2′-pyran-5′,4″-pyrazolone]
scaffolds bearing two tertiary and two quaternary stereocenters. The
Is-MBH alcohol was utilized as an oxa-Michael donor for the first
time as a new approach in highly atom-economical transformations.
This method offered a wide range of bioinspired novel tetrahydro-dispirooxindole-pyran-pyrazolone
derivatives in excellent yields (up to 96%) and diastereoselectivities
(up to >20:1) in a shorter reaction time (15 min)
Diastereo- and Enantioselective Synthesis of 2,2-Disubstituted Benzofuran-3-one Bearing Adjacent Quaternary and Tertiary Stereocenters
The
first highly diastereo- and enantioselective synthesis of armeniaspirol
analogues was achieved using L-proline derived bifunctional
squaramide which outperformed commonly used organocatalysts. Excellent
yield (up to 99%) with diastereoselectivity (up to 99:1) and enantioselectivity
(up to 99%) were obtained for a wide range of substrates
Palladium Catalyzed Asymmetric Allylation of 3‑OBoc-Oxindoles: An Efficient Synthesis of 3‑Allyl-3-hydroxyoxindoles
3-Allyl-3-hydroxyoxindoles
were synthesized in very good enantio-
(up to 97% ee) and diastereoselectivities (dr up to 7.6:1) with contiguous
quaternary and tertiary stereogenic centers by employing tartrate
derived biÂ(oxazoline) in Pd-catalyzed allylation of 3-OBoc-oxindole.
Synthetic utility of 3-allyl-3-hydroxyoxindole was demonstrated by
synthesizing a highly substituted spiroÂ(oxindole-3,2′-tetraÂhydroÂfuran)
derivative in good yield and stereoselectivity