Palladium-Catalyzed Carbon Dioxide Elimination−Fixation Reaction of 4-Methoxycarbonyloxy-2-buten-1-ols

Abstract

A new type of palladium-catalyzed CO(2) recycling reaction using allylic carbonates is described. Reaction of trans-4-methoxycarbonyloxy-2-buten-1-ols in the presence of a palladium catalyst produces cyclic carbonates having a vinyl group via a CO(2) elimination-fixation process. A variety of allylic carbonates participate in the reaction giving cyclic carbonates with high efficiencies. Stereoselective construction of trans-cyclic carbonates is achieved by using nonsymmetric substrates. An enantiospecific reaction proceeds to give chiral cyclic carbonate when a chiral methyl-substituted substrate is subjected to the reaction conditions.

Asymmetric palladium-catalyzed annulation of benzene-1,2-diol and racemic secondary propargylic carbonates bearing two different substituents

“…Using (R)-or (S)-Binap as the chiral ligand gave, respectively, lower and higher ee in the cyclized product, indicating that (S)-Binap/(R)-3a is a match pair, and (R)-Binap/(R)-3a is a mismatch pair. This quite different behaviour between the two mechanisms could be due to the presence of a propargylic hydroxy function in the carbonates used by Yoshida et al, 52,53 function which could stabilize the h 3 -propargylic and h 3 -allylic intermediates by complexation, and so allowing the transfer of chirality.…”

“…The proposed mechanism is different from that of Yoshida and colleagues. 52,53 These authors observed a cascade chirality transfer process in the palladium-catalyzed reaction of substituted chiral propargylic carbonates with phenols, affording chiral cyclic carbonates in a highly enantiospecific manner. If their mechanism is a general one, the reaction of a racemic propargylic carbonate such as 3 or 6 will give the cyclized product as a racemate, even in the presence of a chiral ligand, since no racemization of the different intermediates could occur.…”

Recent Advances in Palladium‐Catalyzed Carboxylation with CO2

“…[18] Both iodobenzene and several aryl and alkenyl halides, such as p-iodotoluene, bromobenzene, p-bromochlorobenzene, p-bromobenzaldehyde, and -bromostyrene, could afford the corresponding alkylidene cyclic carbonates, but the yields were low. [20] The procedure could create a variety of cyclic carbonates through a carbon dioxide elimination/ fixation process with high efficiency. In 1999, Inoue et al achieved the cyclization of propargylic alcohol 93 to prepare alkylidene cyclic carbonates in the presence of CO 2 (Scheme 24).…”

Development of Palladium-Catalyzed Transformations Using Propargylic Compounds

“…With this concept in mind, we attempted to develop a novel methodology for the synthesis of cyclic carbonates including a CO 2 -recycling process using propargylic carbonates with nucleophile. [66][67][68][69][70][71][72][73][74] [66][67][68][69] Our initial attempt at a CO 2 -recycling reaction began using propargylic carbonate 36a, having a hydroxyl group at another propargylic position, with a soft nucleophile. After several attempts, we found the desired reaction proceeds when phenols were used as the nucleophile.…”