An Asymmetric Allylic Alkylation–Smiles Rearrangement–Sulfinate Addition Sequence to Construct Chiral Cyclic Sulfones

An asymmetric allylic alkylation of Morita–Baylis–Hillman carbonates and β-keto sulfones was investigated by the catalysis of modified cinchona alkaloids, whose products underwent a Smiles rearrangement–sulfinate addition cascade to furnish highly functionalized five-membered cyclic sulfones in moderate to excellent enantioselectivity and good diastereoselectivity after treatment with DBU

An Asymmetric Allylic Alkylation–Smiles Rearrangement–Sulfinate Addition Sequence to Construct Chiral Cyclic Sulfones

An asymmetric allylic alkylation of Morita–Baylis–Hillman carbonates and β-keto sulfones was investigated by the catalysis of modified cinchona alkaloids, whose products underwent a Smiles rearrangement–sulfinate addition cascade to furnish highly functionalized five-membered cyclic sulfones in moderate to excellent enantioselectivity and good diastereoselectivity after treatment with DBU

Stereodivergence in Amine-Catalyzed Regioselective [4 + 2] Cycloadditions of β‑Substituted Cyclic Enones and Polyconjugated Malononitriles

Switchable reaction patterns of β-substituted cyclic enones via amine-based dienamine activation are reported. While γ-regioselective vinylogous Michael addition was observed with alkylidenemalononitriles, a completely different [4 + 2] cycloaddition was obtained with allylidene- or alkynylidenemalononitrile substrates, affording densely substituted bicyclo[2.2.2]­octanes or analogous architectures with moderate to excellent diastereo- and enantioselectivity by the catalysis of primary amines from natural quinidine or quinine. Importantly, high diastereodivergence was achieved through unusual hydrogen-bonding interactions of multifunctional primary-amine catalytic systems. Endo cycloadducts were efficiently produced using a combination of 9-amino-9-deoxyepiquinidine and salicylic acid, while exo variants were obtained using 6′-hydroxy-9-amino-9-deoxyepiquinidine. Moreover, we successfully isolated the Michael addition intermediates in some cases, indicating that the above [4 + 2] reaction via dienamine catalysis may proceed by a stepwise Michael–Michael cascade rather than by a concerted Diels–Alder cycloaddition pathway

Stereodivergence in Amine-Catalyzed Regioselective [4 + 2] Cycloadditions of β‑Substituted Cyclic Enones and Polyconjugated Malononitriles

Switchable reaction patterns of β-substituted cyclic enones via amine-based dienamine activation are reported. While γ-regioselective vinylogous Michael addition was observed with alkylidenemalononitriles, a completely different [4 + 2] cycloaddition was obtained with allylidene- or alkynylidenemalononitrile substrates, affording densely substituted bicyclo[2.2.2]­octanes or analogous architectures with moderate to excellent diastereo- and enantioselectivity by the catalysis of primary amines from natural quinidine or quinine. Importantly, high diastereodivergence was achieved through unusual hydrogen-bonding interactions of multifunctional primary-amine catalytic systems. Endo cycloadducts were efficiently produced using a combination of 9-amino-9-deoxyepiquinidine and salicylic acid, while exo variants were obtained using 6′-hydroxy-9-amino-9-deoxyepiquinidine. Moreover, we successfully isolated the Michael addition intermediates in some cases, indicating that the above [4 + 2] reaction via dienamine catalysis may proceed by a stepwise Michael–Michael cascade rather than by a concerted Diels–Alder cycloaddition pathway

Stereodivergence in Amine-Catalyzed Regioselective [4 + 2] Cycloadditions of β‑Substituted Cyclic Enones and Polyconjugated Malononitriles

Switchable reaction patterns of β-substituted cyclic enones via amine-based dienamine activation are reported. While γ-regioselective vinylogous Michael addition was observed with alkylidenemalononitriles, a completely different [4 + 2] cycloaddition was obtained with allylidene- or alkynylidenemalononitrile substrates, affording densely substituted bicyclo[2.2.2]­octanes or analogous architectures with moderate to excellent diastereo- and enantioselectivity by the catalysis of primary amines from natural quinidine or quinine. Importantly, high diastereodivergence was achieved through unusual hydrogen-bonding interactions of multifunctional primary-amine catalytic systems. Endo cycloadducts were efficiently produced using a combination of 9-amino-9-deoxyepiquinidine and salicylic acid, while exo variants were obtained using 6′-hydroxy-9-amino-9-deoxyepiquinidine. Moreover, we successfully isolated the Michael addition intermediates in some cases, indicating that the above [4 + 2] reaction via dienamine catalysis may proceed by a stepwise Michael–Michael cascade rather than by a concerted Diels–Alder cycloaddition pathway

Aminocatalytic Asymmetric <i>exo</i>-Diels–Alder Reaction with Methiodide Salts of Mannich Bases and 2,4-Dienals to Construct Chiral Spirocycles

An asymmetric <i>exo</i>-Diels–Alder reaction of α-methylene carbonyl compounds, generated in situ from stable methiodide salts of Mannich bases, with 2,4-dienals, has been developed through trienamine activation of a chiral secondary amine. A spectrum of spirocyclanes with high molecular complexity was efficiently constructed in moderate to excellent diastereo- and enantioselectivity

Aminocatalytic Asymmetric <i>exo</i>-Diels–Alder Reaction with Methiodide Salts of Mannich Bases and 2,4-Dienals to Construct Chiral Spirocycles

An asymmetric <i>exo</i>-Diels–Alder reaction of α-methylene carbonyl compounds, generated in situ from stable methiodide salts of Mannich bases, with 2,4-dienals, has been developed through trienamine activation of a chiral secondary amine. A spectrum of spirocyclanes with high molecular complexity was efficiently constructed in moderate to excellent diastereo- and enantioselectivity

1‑Azadienes as Regio- and Chemoselective Dienophiles in Aminocatalytic Asymmetric Diels–Alder Reaction

Electron-deficient 1-aza-1,3-butadienes containing a 1,2-benzoisothiazole-1,1-dioxide or 1,2,3-benzoxathiazine-2,2-dioxide motif act as regio- and chemoselective dienophiles in normal-electron-demand Diels–Alder reactions with HOMO-raised trienamines, rather than typical 4π-participation in inverse-electron-demand versions. The enantioenriched cycloadducts could be efficiently converted to spiro or fused frameworks with high structural and stereogenic complexity by a sequential aza-benzoin reaction or other transformations

Asymmetric Diels–Alder Reaction of 2‑Methyl-3-indolylmethanols via in Situ Generation of <i>o</i>‑Quinodimethanes

An asymmetric Diels–Alder reaction of 2-methyl-3-indolylmethanols and α,β-unsaturated aldehydes has been developed that relies on in situ generation of active indole-2,3-quinodimethane intermediates under mild acidic conditions and uses a secondary chiral amine as iminium activation catalyst. An array of highly enantioenriched tetrahydrocarbazoles have been efficiently produced in fair to good yields

Asymmetric Diels–Alder Reaction of 2‑Methyl-3-indolylmethanols via in Situ Generation of <i>o</i>‑Quinodimethanes

An asymmetric Diels–Alder reaction of 2-methyl-3-indolylmethanols and α,β-unsaturated aldehydes has been developed that relies on in situ generation of active indole-2,3-quinodimethane intermediates under mild acidic conditions and uses a secondary chiral amine as iminium activation catalyst. An array of highly enantioenriched tetrahydrocarbazoles have been efficiently produced in fair to good yields