Highly stereoselective and catalytic desulfitative C O and C I dienylation with sulfolenes: The importance of basic additives

Abstract

Conjugated dienes and polyenes are central structural motifs of natural products, and key synthetic intermediates in organic synthesis and materials science. We describe herein a palladium-catalyzed dienylation of aryl, heteroaryl, and vinyl triflates, nonaflates and iodides that were previously identified as recalcitrant substrates for the sulfolene-mediated catalytic dienylation. The method has now been successfully expanded to CO and C-I dienylation, demonstrating broad scope with respect to sulfonates, iodides and sulfolenes. The reactions proceed with high regio-and stereoselectivity, and efficiency that are strongly influenced by basic additives, whose influence on the reaction performance was systematically studied.

Desulfonylative Transformations of Sulfones by Transition-Metal Catalysis, Photocatalysis, and Organocatalysis

“…In 2019, Larionov employed sulfolenes as new dienylating agents for the synthesis of arylated dienes with high stereoselectivity (Scheme ). Pd­(OAc) 2 /dppbz was found to be the optimal catalyst, and KOMe was an effective base for the in situ generation of dienyl sulfinate by the ring opening of sulfolenes. This method produces complex arylated dienes 88 from substituted sulfolenes 86 and arylhalides 87 in good to excellent yields.…”

Catalytic Dienylation: An Emergent Strategy for the Stereoselective Construction of Conjugated Dienes and Polyenes

“…The scope of the reaction was further extended to (hetero)aryl sulfonates by the replacement of potassium methoxide with potassium tert-butoxide and potassium carbonate with potassium bicarbonate. 15 Aryl iodides were found to be recalcitrant under the optimized reaction conditions but underwent the dienylation with silver oxide as a basic additive in place of potassium bicarbonate. Interestingly, the stereoselectivity of the dienylation with the unsubstituted sulfolene can be inverted to >30:1 in favor of the 1Z-diene when Xantphos is used as a ligand instead of dppbz (Scheme 3).…”

“…The scope of the reaction was further extended to (hetero)aryl sulfonates by the replacement of potassium methoxide with potassium tert-butoxide and of potassium carbonate with potassium bicarbonate. 15 Aryl iodides were found to be recalcitrant under the optimized reaction conditions but underwent the dienylation with silver oxide as a basic additive in place of potassium bicarbonate.…”

Recent advances in the application of ligands in palladium-catalyzed chemoselective coupling reactions at C–Br, C–OTf, and C–Cl sites

“…Bidentate phosphine palladium is a versatile catalytic system used in cross-coupling reactions. Fifteen published examples 17–20,42,53,82–90 in bromoaryl triflate substrates (Table 11) and more than 40 examples 82,84,86–128 demonstrated remarkable O -triflyl-selectivity in chemoselective entries among chloroaryl triflates (Table 12). In spite of the variations in the specific substrates and reaction conditions used in the reported examples, the general chemoselectivity trend of bidentate phosphine ligand systems remains consistent toward the selectivity at triflates, where C–OTf > C–Br > C–Cl.…”