Domino Reaction for the Synthesis of Substituted Pyrano[3',4':3,4]cyclopenta[1,2-c]chromenes Involving Double Ring Formation

Herein, we present a green cascade approach for synthesizing a range of chemoselective polysubstituted pyrano[3',4':3,4]cyclopenta[1,2-c]chromenes containing a chiral stereocenter. The strategy involves a metal-free nucleophilic reaction between dialkyl (2E)-2-{2-oxo-3-[(2E)-3-aryl-2-propenoyl]-2H-chromen-4-yl}-2-butenedioates and α,α-dicyanoolefins under reflux conditions in ethanol solvent. Mechanistic studies have shown that the reaction proceeds via a cascade of steps, including Michael addition, intramolecular C- and O-cyclization, intramolecular trans-esterification, [1,2]-H and [1,5]-methoxy- and ethoxy carbonyl shift, and finally aromatization to yield the desired product. In this method, three bonds (2C-C and C-O) form in one pot, simultaneously forming two new cyclopentane and pyrano rings by double cyclization reactions. Other advantages of this method are that it has a simple operation, readily available starting materials, a chemoselective cascade process, transition metal-free, synthetically useful yields, and green conditions by using ethanol as a solvent.

Metal-free synthesis of α-acyloxy ketones from carboxylic acids and sulfoxonium ylides

A straightforward, catalyst- and additive-free approach has been described for synthesizing α-acyloxy ketones from β-ketosulfoxonium ylides and carboxylic acids. Moderate to high yields of α-acyloxy ketones were produced using sulfoxonium ylides and carboxylic acids adorned with various functional groups. Eventually, the applicability of this approach has been shown via a large-scale reaction and transforming the synthesized α-acyloxy ketone derivatives into other valuable compounds.

A Three-Step Process to Facilitate the Enantioselective Assembly of Cis-Fused Octahydrophenanthrenes with a Quaternary Stereocenter

A three-step process for the enantioselective assembly of cis-fused octahydrophenanthrenes with a quaternary stereocenter is reported. This synthetic strategy relies on a regioselective γ-alkylation, a one-pot sequence of asymmetric hydrogenation and oxidation, and an intramolecular enolate arylation to facilitate the rapid and enantioselective construction of cis-fused octahydrophenanthrene scaffolds with an arylated all-carbon quaternary stereocenter concisely and efficiently.

Recent advances in the synthesis of cyclic compounds using α,α-dicyanoolefins as versatile vinylogous nucleophiles

This article provides a review of the applications of α,α-dicyanoolefins as versatile vinylogous nucleophiles in the synthesis of various cyclic compounds, covering the literature from the past 13 years.

Decarboxylative Oxyacyloxylation of Propiolic Acids: Construction of Alkynyl-Containing α-Acyloxy Ketones

Novel decarboxylative oxyacyloxylation of propiolic acids has been developed. This reaction provides an efficient access to alkynyl-containing α-acyloxy ketones from readily available starting materials and exhibits significant functional group tolerance. Furthermore, oxyacyloxylation of terminal alkynes and aliphatic propiolic acids was also developed. A possible reaction mechanism is proposed based on mechanistic studies.

Tetrahydrobenzochromene Synthesis Enabled by a Deconjugative Alkylation/Tsuji-Saegusa-Ito Oxidation on Knoevenagel Adducts

A modular and practical route to versatile cyano-1,3-dienes by a sequence involving deconjugative alkylation and "Tsuji-Saegusa-Ito oxidation" is reported. In this letter, the versatility of the products is also explored, including a route to benzochromene scaffolds common to many natural products.

Visible light catalyzed reaction of α-bromochalcones with chalcones: direct access to the urundeuvine scaffold

The α-keto vinyl radicals generated from α-bromochalcones under visible light photoredox catalyzed conditions were trapped by chalcones.

Recent methods for the synthesis of α-acyloxy ketones

The present review provides a broad description of the methods reported for the synthesis of α-acyloxy ketones and some of their derivatives.

Factors Governing and Application of the Cope Rearrangement of 3,3-Dicyano-1,5-dienes and Related Studies

Cope and co-workers reported the [3,3] rearrangement of 3,3-dicyano-1,5-dienes in the early 1940s ("The Cope rearrangement"). However, these original substrates have remained largely unstudied until recently. Herein we explore styrene-deconjugating Cope rearrangements, a diastereoselective Cope rearrangement/deconjugative α-allylation sequence, and factors governing α- vs γ-allylation regioselectivity of Knoevenagel adduct allyl anions. Ultimately, these studies result in the synthesis of diverse and functionally dense polycycloalkane frameworks from abundant reagents using simple chemistry.