Chelation-controlled, palladium-catalyzed vinylic substitution reactions of vinyl ethers. 2-Arylethanal equivalents from aryl halides

Direct Synthesis of Protected Arylacetaldehydes by Tetrakis(phosphane)palladium‐Catalyzed Arylation of Ethyleneglycol Vinyl Ether

“…[18] It has been demonstrated that the regioselectivity of the addition of organopalladium intermediates can be influenced by coordinating groups adjacent to the substrate double bond. [19][20][21][22][23][24] For example, Hallberg et al have described that the nitrogen-containing vinyl ether [2-(dimethylamino)ethoxy]ethene undergoes regioselective β-arylation with several aryl halides in the presence of palladium acetate. [19,21] On the other hand, in the presence of ethylene glycol vinyl ether with Pd(OAc) 2 /dppp as catalyst, they obtained selective α-arylations to give aryl vinyl ethers, which undergo subsequent ketalisation to form selectively the isomer e shown in Scheme 1.…”

Terminal Heck Vinylations of Chelating Vinyl Ethers

“…Dimethylaminoethyl vinyl ether 1a was prepared according the literature procedure. [8] (S)-N-Methyl-2-vinyloxymethylpyrrolidine (1c)…”

“…[24] Discussion Mechanism In a chelation-controlled terminal Heck vinylation process the reaction route exemplified in Scheme 5 appears reasonable. [8,25,26] Starting from vinyl triflates, cationic intermediates should prevail from the oxidative addition complex A and onwards. [6,27 -29] The chelated ring size controls the direction of insertion into p-complex B and provides the s-alkylpalladium complex C with high b-selectivity.…”

“…[8,9] In these reactions the specific introduction of an appropriately designed palladium(II)-coordinating tertiary amino group into the olefin allowed an efficient substrate presentation and a high terminal regiocontrol. [10] Employing a cyclic vinyl ether with a chiral N-methylpyrrolidine group, highly diastereoselective b-arylations were realized.…”

Directed Mizoroki–Heck Reactions

“…With regard to synthetic usefulness, the intramolecular Mizoroki-Heck reaction has undoubtedly outshone many other efforts in the wide-ranging area of MizorokiHeck chemistry. One of these underappreciated areas, which has recently been going through a second childhood, was systematically introduced by Hallberg several years ago [23][24][25][26]. In order to control the regioselectivity of an intermolecular Mizoroki-Heck reaction, Hallberg designed an alternative to intramolecular Mizoroki-Heck processes by installation of a suitable donor Do in the alkene fragment 2 (2 ⇒ 4, Fig.…”