- Palladium-Catalyzed Methylation of Aryl, Heteroaryl, and Vinyl Boronate Esters
-
A method for the direct methylation of aryl, heteroaryl, and vinyl boronate esters is reported, involving the reaction of iodomethane with aryl-, heteroaryl-, and vinylboronate esters catalyzed by palladium and PtBu2Me. This transformation occurs with a remarkably broad scope and is suitable for late-stage derivatization of biologically active compounds via the boronate esters. The unique capabilities of this method are demonstrated by combining carbon-boron bond-forming reactions with palladium-catalyzed methylation in a tandem transformation.
- Haydl, Alexander M.,Hartwig, John F.
-
supporting information
p. 1337 - 1341
(2019/02/26)
-
- The photochemical alkylation and reduction of heteroarenes
-
The functionalization of heteroarenes has been integral to the structural diversification of medicinally active molecules such as quinolines, pyridines, and phenanthridines. Electron-deficient heteroarenes are electronically compatible to react with relatively nucleophilic free radicals such as hydroxyalkyl. However, the radical functionalization of such heteroarenes has been marked by the use of transition-metal catalyzed processes that require initiators and stoichiometric oxidants. Herein, we describe the photochemical alkylation of quinolines, pyridines and phenanthridines, where through direct excitation of the protonated heterocycle, alcohols and ethers, such as methanol and THF, can serve as alkylating agents. We also report the discovery of a photochemical reduction of these heteroarenes using only iPrOH and HCl. Mechanistic studies to elucidate the underlying mechanism of these transformations, and preliminary results on catalytic methylations are also reported.
- McCallum,Pitre,Morin,Scaiano,Barriault
-
p. 7412 - 7418
(2017/10/31)
-
- Diacylation of alkenes catalyzed by sulfonic acids 3: application of weak sulfonic acids to the regioselective synthesis of pyrylium salts from isoolefins and linear olefins
-
The use of weak sulfonic acids (methanesulfonic and α-carboxyalkanesulfonic acids) as catalysts in diacylation of disymmetrical isoalkenes by carboxylic acid anhydrides afford almost exclusively the more substituted pyrylium salt.Particularly, simple isoalkenes (generated in situ from dimethyl alkyl carbinols) and citronellol lead 2,3,4,6-tetrasubstituted pyrylium salts in high yields.Diacylation of 1-alkenes lead to 2,3,6-trialkyl-substituted pyrylium without isomerization but in low yield.The observed lower regioselectivities in comparative reactions catalyzed by strong protonic acids (perchloric acid or trifluoromethanesulfonic acid which are the classical catalysts in this kind of synthesis) confirm that the strenght of the catalyst governs the regioselectivity of the diacylation of olefins when carboxylic acid anhydrides are used as sources of acylating agents.In all cases, the obtained pyrylium salts were transformed into the corresponding pyridines by treatment with concentrated ammonia.
- Rajoharison, Harivelo G.,Roussel, Christian
-
p. 307 - 313
(2007/10/02)
-