Diastereoselective desymmetrization reactions of prochiral para-quinamines with cyclopropenes generated in situ: access to fused hydroindol-5-one scaffolds.

Interesting desymmetric [3 + 2] annulation reactions between p-quinamines as prochiral N-donors and 2-aroyl-1-chlorocyclopropanecarboxylates facilitated by a base are reported. This successive double Michael reaction delivered a unique class of cyclopropane-fused hydoindol-5-one frameworks, each having four contiguous stereogenic centers, with three of them being fully substituted. Moreover, this method was found to provide acceptable chemical yields with promising diastereoselectivities (dr of up to ≤95 : 5) and to work with a variety of substrates.

Substrate-Controlled Domino Reaction of -Sulfonyl Ketimines with 2-Aroyl-1-chlorocyclopropanecarboxylates: Access to Cyclopenta[]chromenes and Benzo[]cyclopenta[][1,2]thiazepine Dioxides.

An unprecedented substrate-controlled annulation method for the synthesis of fascinating classes of angularly fused cyclopenta[]chromenes and benzo[]cyclopenta[][1,2]thiazepine 5,5-dioxide derivatives in good to high chemical yields is reported. This Michael-initiated ring-expansion reaction would enable two C-C and one C-O or C-N bonds by a judicious choice of carbonucleophiles, either 4-alkyl or 3-alkyl-substituted -sulfonyl ketimines, respectively, with a series of donor-acceptor cyclopropane scaffolds as 4C sources promoted by DBU. Moreover, this eco-friendly method is mild enough to protect different kinds of functionalities.

NHOAc-Promoted Domino Route to Hydroxyarylated Unsymmetrical Pyridines under Neat Conditions.

A new metal-, oxidant-, and solvent-free ecofriendly domino method has been established for modular synthesis of a diverse range of medicinally promising hydroxyarylated unsymmetrical pyridines in good to high chemical yields with an excellent regioselectivity. This domino process involves a range of -sulfonyl ketimines as C,N-binucleophiles, enolizable ketones, and aromatic/heteroaromatic aldehydes using ammonium acetate as an ideal promoter under neat conditions, which creates two new C-C bonds and one C-N bond. Notably, the neutral reaction conditions are mild enough to tolerate a range of functionalities and cover a variety of substrates, thus bestowing a powerful avenue to access tri- and tetrasubstituted pyridines including carbo- and heterocyclic fused ones.