Catalyst-Free, Room-Temperature Accessible Regioselective Synthesis of Spiroquinolines and Their Antioxidant Study

An efficient, regioselective, and environmentally benign approach was established using the multicomponent reaction-based synthesis of novel antioxidant spiroquinoline derivatives such as spiro[dioxolo[4,5-g]quinoline], spiro[dioxino[2,3-g]quinoline], and spiro[pyrazolo[4,3-f]quinoline] by reaction of aryl aldehyde, Meldrum's acid, and amine derivatives under an additive-free reaction in aqueous ethanol. Here, two asymmetric carbon centers, three new C-C bonds, and one C-N bond are developed in the final motif. This synthetic methodology offers excellent yields with an easy workup procedure, high diastereoselectivity [d.r. >50:1 (cis/trans)], admirable atom economy, and low E-factor values. Synthesized spiro compounds were investigated for their in vitro antioxidant activity by 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays. In the ABTS radical scavenging assay, compounds 4d, 4f, and 4l exhibit excellent potency, and in the DPPH radical scavenging assay, compounds 4a, 4d, 4f, and 4g, exhibit excellent potency.

Progress in the Chemistry of Tetrahydroquinolines

Tetrahydroquinoline is one of the most important simple nitrogen heterocycles, being widespread in nature and present in a broad variety of pharmacologically active compounds. This Review summarizes the progress achieved in the chemistry of tetrahydroquinolines, with emphasis on their synthesis, during the period from mid-2010 to early 2018.

Ring strain-dictated divergent fluorinating Prins cyclization or semipinacol rearrangement

We have developed ring-strain dictated divergent diastereoselective fluorinating Prins cyclizations or semipinacol rearrangements to access a range of tetrahydropyran derivatives.

A novel self-terminated Prins strategy for the synthesis of tetrahydropyran-4-one derivatives and their behaviour in Fisher indole synthesis

A novel self-terminated Prins strategy has been developed for the synthesis of 2-substituted tetrahydropyran-4-one derivatives through a condensation of 3-(phenylthio)but-3-en-1-ol with carbonyl compounds in the presence of 5 mol% of Sc(OTf)₃ under mild conditions.