Ruthenium-Catalyzed 1,6-Hydroalkylation of para-Quinone Methides with Ketones via the in Situ Activation of C(sp3)-H Bonds

A simple and efficient method for the ruthenium-catalyzed 1,6-hydroalkylation of para-quinone methides (p-QMs) with ketones via the in situ activation of C(sp3)-H bonds has been disclosed. Without the need for preactivation of the substrates and oxidant, a broad range of p-QMs and ketones are well tolerated, producing the expected 1,6-hydroalkylation products with moderate to good yields. Step-by-step control experiments and DFT calculation were conducted systematically to gain insights for the plausible reaction mechanism. This finding may have potential application in the selective diarylmethylation of ketones at the α-C position in organic synthesis.

Design and development of intramolecular doubly vinylogous Michael addition to access 3-aryl substituted 2-alkenyl-benzofurans and -indoles

Herein, we have disclosed a rare example of an intramolecular doubly vinylogous Michael addition (DVMA). The reaction design exploits the innate reactivity of ortho-heteroatom substituted para-quinone methide (p-QM) derivatives. The sequential reaction of p-QMs and activated allyl halides proceeds through heteroatom-allylation, DVMA and oxidation to furnish a diverse range of 2-alkenyl benzofuran and 2-alkenyl indole derivatives in high yields.

Diastereoselective synthesis of polycyclic indolines via dearomative [4 + 2] cycloaddition of 3-nitroindoles with ortho-aminophenyl p-quinone methides

A formal [4 + 2] cycloaddition of 3-nitroindoles with ortho-aminophenyl p-quinone methides via a dearomatization process was developed. This method provides a facile approach for preparing tetrahydro-5H-indolo[2,3-b]quinolones with good results. With the bifunctional Cinchona alkaloid-squaramide as the catalyst, the asymmetric version of the reaction successfully afforded the corresponding chiral products with moderate to good enantioselectivities. This work represents the first dearomative cycloaddition of electron-deficient heteroarenes triggered by aza-Michael addition from p-QMs.

Organocatalytic Asymmetric Synthesis of Tetrahydroquinolines from ortho-Aminophenyl para-Quinone Methides

The asymmetric catalytic [4 + 2] cycloannulation of ortho-aminophenyl p-QMs with different types of alkenes for the construction of tetrahydroquinolines containing three contiguous stereogenic centers was developed. This is the first example of catalytic asymmetric cycloannulation of ortho-aminophenyl p-QMs. This reaction exhibits excellent functional group tolerance. Excellent yields, exclusive diastereoselectivities, and high enantioselectivities were obtained in this efficient organocatalytic reaction.

Multicomponent Synthesis of S-Benzyl Dithiocarbamates from para-Quinone Methides and Their Biological Evaluation for the Treatment of Alzheimer's Disease

Multicomponent synthesis of biologically relevant S-benzyl dithiocarbamates from para-quinone methides, amines, and carbon disulfide are described under catalyst and additive-free conditions. The reactions proceeded at room temperature in a short span of time with excellent yields. One of the synthesized compounds, 3e showed considerable acetylcholinesterase (AChE) inhibitory (51.70 + 5.63% at 20 μm) and antioxidant (63.52 ± 1.15 at 20 μm) activities.

Tandem 1,6-addition/cyclopropanation/rearrangement reaction of vinylogous para-quinone methides with 3-chlorooxindoles: construction of vicinal quaternary carbon centers

A novel tandem 1,6-addition/cyclopropanation/rearrangement reaction of vinylogous para-quinone methides with 3-chlorooxindoles has been developed, providing dispirooxindole–cyclopentane–cyclohexadienones with vicinal quaternary carbon centers.