Carbon−Carbon Bond Formation in Palladium(II)-Catalyzed Allylic Oxidation:  A Novel Oxidative Carbocyclization of Allene-Substituted Olefins

Abstract

A new efficient palladium(II)-catalyzed oxidative carbocyclization has been developed. It was found that allene-substituted olefins 1 cyclized in the presence of 1 mol % Pd(O2CCF3)2 and p-benzoquinone (2 equiv) to give bicyclic ring systems 2 in good to excellent yields. The cyclization constitutes a new type of carbon-carbon bond forming reaction between an allene and an olefin under oxidative conditions.

Aerobic Oxidations Catalyzed by Zeolite‐Encapsulated Cobalt Salophen

“…Our group has previously reported the oxidative cyclization of ene-allenes catalyzed by Pd(II) and with BQ as stoichiometic oxidant. [21] More recently, this work has been extended by employing a triple catalytic system enabling the use of O 2 as terminal oxidant and with an iron(II) phthalocyanine as oxygen activating catalyst and a catalytic amount of BQ. [12] The bicyclic product was formed in high yield when the reaction was carried out in toluene at 95 8C.…”

Palladium Pincer Complex‐Catalyzed Condensation of Sulfonimines and Isocyanoacetate to Imidazoline Derivatives. Dependence of the Stereoselectivity on the Ligand Effects

“…Jan is a great friend and colleague and with this paper, we would like to congratulate him to the 60 th birthday as well as show our appreciation of his great achievements in metal and bio-catalysis, in particular in palladium chemistry. [1][2][3][4][5][6][7][8][9][10][11][12] Catalytic applications of palladium pincer complexes [13][14][15][16][17][18][19] (e.g., 1a-g) have attracted considerable attention in the last couple of years, [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] since employment of pincer complex catalysts in place of the commonly used palladium salts often opens new and highly selective synthetic routes. Furthermore, palladium pincer complexes are highly stable and robust catalysts because of a tight terdentate coordination of the ligand to the metal center.…”

Palladium‐Catalyzed Oxidative Acyloxylation/Carbocyclization of Allenynes

“…[7] In connection with our previous studies on acetoxylation(hydroxylation)/carbocyclizations of dienallenes (Scheme 1 a), [4] we envisioned an oxidative acetoxylation/carbocyclization of allenynes 1 in the presence of HOAc/ LiOAc, with a simple Pd II salt as the catalyst (Scheme 1 b). Based on the previously proposed mechanism, [4,5] the reaction was expected to be initiated by allene attack on Pd II through allylic C À H bond cleavage followed by alkyne insertion to give acetoxylated triene product 2. However, the reaction took an unexpected path, and herein we report on a palladium-catalyzed oxidative acyloxylation/carbocyclization of allenynes 1 to give acyloxylated vinylallenes 3 (Scheme 1 b).…”

“…[1][2][3][4][5] In particular, oxidative carbocyclization strategies have been efficiently applied to total synthesis.…”

“…[1][2][3][4][5] In particular, oxidative carbocyclization strategies have been efficiently applied to total synthesis. [3] As a continuation of our research on the palladium-catalyzed oxidative carbocyclizations of dienallenes [4] and enallenes, [5] we recently developed palladium-catalyzed arylating or borylating oxidative carbocyclizations of allenynes [6] by using the corresponding arylboronic acid or B 2 pin 2 . [7] In connection with our previous studies on acetoxylation(hydroxylation)/carbocyclizations of dienallenes (Scheme 1 a), [4] we envisioned an oxidative acetoxylation/carbocyclization of allenynes 1 in the presence of HOAc/ LiOAc, with a simple Pd II salt as the catalyst (Scheme 1 b).…”