Spirocyclopropanation Reaction of para-Quinone Methides with Sulfonium Salts: The Synthesis of Spirocyclopropanyl para-Dienones

Abstract

A novel DBU-mediated stereoselective spirocyclopropanation of para-quinone methides with sulfonium salts has been developed on the basis of the mode involving a 1,6-conjugate addition/intramolecular dearomatizing cyclization cascade. This reaction provides a mild and effective method for the assembly of synthetically and structurally interesting spirocyclopropanyl para-dienones. The feasibility for the enantioselective access to such functionalized para-dienones has also been explored by using the axially chiral sulfonium salt. Importantly, the regioselective ring openings of the related spirocyclopropanyl para-dienones have been achieved divergently.

Enhancing the Reduction Potential of Quinones via Complex Formation

“…This result is due to the poor proton-donating ability of this amine. Its H-bonding energy with even the anionic semiquinone (9-10 kcal/mol) is smaller than the strong association energy of the amine in its stacked arrangement with the corresponding neutral quinones (13)(14) kcal/mol).…”

“…7 Similarly, quinone compounds have a wide range of application in synthetic chemistry, catalysis, and electrochemistry. [8][9][10][11][12][13][14] Active research continues to assess the usefulness of quinone in lithium-O2 batteries. [15][16][17] Quinones are very good oxidizing agents and can undergo one or two electron reduction, forming monoanion and dianion radical, respectively, depending on the conditions.…”

Formal [2+1] Annulation (Spiro‐Cyclopropanation) Reaction between Sulfur Ylides Derived from Baylis‐Hillman Bromides and Arylidene Indane‐1,3‐Dione

“…Ylides are one of the promising substrates in the last category as they can serve as the suitable nucleophilic components containing a leaving group as well . Very recently, base‐mediated stereoselective spiro‐cyclopropanation of para ‐quinone methide has been reported in the presence of stable sulfonium salt …”

Salts in Organic Synthesis: An Overview and Their Diversified Use

“…Various papers are published by discussing the role of individual salts, their selective way of transformation, role in asymmetric synthesis and many more. Some of the recent influencing research on application of salts in organic synthesis are use of diaryliodonium salts for novel arylation [20], applications of ferrocenium salts [21], salt as linker source [22], pyridinium salts as radical reservoir [23], use of vinyliodonium salts for alkenylation of nitriles [24], use of sulfonium salts for synthesis of spirocyclopropanyl paradienones [25], use of phosphonium salts for selective functionalization of pyridines [26], tropylium salts as lewis acid to catalyze acetalization and transacetalization [27], use of Phenyltrimethylammonium salts in nickel-catalyzed methylation of C− H bonds [28], aryldiazonium salts for carbohydroxylation of styrenes [29], synthesis of bicyclic aziridines from pyridinium salts [30], nucleophilic arylation with tetraarylphosphonium salts [31], application of trimethylsilanolate alkali salts in organic synthesis [32], use of α, β-unsaturated acylammonium salts for asymmetric organocatalysis [33], review on cesium salts use in organic synthesis [34], iodonium salts as benzyne precursors [35], use of bunte salts as a sulfur source for synthesis of 3-thioindoles [36], and C− H functionalization of arenes by diaryliodonium salts [37] etc.…”