Stereoselective Synthesis of Tri- and Tetrasubstituted Olefins via 1,6-Additions of Diazo Compounds and Their Precursors to p-Quinone Methides

Abstract

Reactions of para-quinone methides (p-QMs) with α-diazo-β-ketosulfones and their corresponding esters as well as simple β-dicarbonyl compounds and β-ketosulfones have been carried out under basic conditions. While the reaction of diazosulfone with p-QMs afforded trisubstituted olefins via deacylative 1,6-addition and elimination, α-diazo-β-ketoesters and various active methylene compounds such as 1,3-dicarbonyls and β-ketosulfones afforded tetrasubstituted olefins via 1,6-addition and aerial oxidation. These simple, environmentally benign, and mechanistically diverse protocols provided the products in moderate to excellent yields and selectivities.

2 + 2 = 3: Making Ternary Phases through a Binary Approach

“…In the world of solution chemistry, mechanistic studies offer invaluable information about the reason certain reactions provide the desired result and why others do not. − Through a combination of experimental and computational studies, the rationale behind unique aspects of a reaction pathway such as site reactivity or stereoselectivity can be elucidated. , In addition to providing information about the reaction at hand, these studies can allow for the assessment of possible applications of the reaction to other systems. Because of the relatively low temperatures and self-contained nature of solution reactions, taking aliquots for qualitative or quantitative evaluation through the course of the reaction is easily accessible in many cases.…”

Reactivity of quinone methides with carbenes generated from α-diazocarbonyl compounds and related compounds

“…Later, the same group reported the single-step synthesis of tri-and tetrasubstituted alkenes from a-diazo-b-ketosulfone and a-diazo-b-carbonyl compounds with p-QMs (Schemes 24 and 25). 40…”

“…Later, the same group reported the single-step synthesis of tri- and tetrasubstituted alkenes from α-diazo-β-ketosulfone and α-diazo-β-carbonyl compounds with p -QMs (Schemes 24 and 25). 40 A wide variety of tri- and tetrasubstituted alkenes 144 and 152 were synthesized through the initial 1,6-conjugate addition of α-diazo-β-ketosulfone 143 and α-diazo-β-dicarbonyl 151 compounds to p -QMs. Subsequent protonation and the elimination of nitrogen delivered the corresponding alkenes with good to excellent yields and selectivity in the absence of a rhodium-catalyst (Schemes 24 and 25).…”

One-Step Protocol for the Synthesis of Cyanoacrylates Promoted by Elemental Sulfur from p-Quinone Methides and Cyanoacetates under Basic Conditions

“…Then, Namboothiri and Mohanan, respectively, described Rh-catalyzed diazo group elimination and 1,2-migration of the phenolic group to afford trisubstituted alkenes from diazo adducts achieved by the reaction of diazoesters with p -QMs under KOH (Scheme b). Subsequently, in 2021, Namboothiri’s group published a base-promoted protocol for the synthesis of tri- and tetrasubstituted alkenes by both deacylative and nondeacylative 1,6-addition of α-diazocarbonyl compounds and their precursors to the p -QMs under transition metal-free conditions again (Scheme c). However, though we were urged by these desired research results from p -QMs, we found that these methods to afford arylated olefins still resulted in the limitations of their broad application such as the use of great amount of base (4 equiv), the stability of diazo compounds, the cost of noble metals, low temperature (−20 °C), the application of TiCl 4 , and environmental unfriendliness, which will still be big problems that cannot be ignored and can restrict seriously further development of protocols.…”