Palladium‐Catalyzed Annulation of Aryl‐1,2‐diols and Propargylic Carbonates. Theoretical Study of the Observed Regioselectivities

Abstract

Methyl 1-methylprop-2-ynyl carbonate reacts with 3-and 4-substituted benzene-1,2-diols to give 2,3-dihydro-3-methyl-2-methylidene-1,4-benzodioxines, as a mixture of regioisomers in the case of methoxy-substituted diphenol, and a single regioisomer for the nitro-and the formyl-substituted diphenols. The oxyanion which attacks first corresponds to the less acidic hydroxy function, and the attack of the second oxyanion on the η 3 -allylpalladium intermediate is directed toward the more substituted carbon atom. In order to explain

Quantitative Determination of the Regioselectivity of Nucleophilic Addition to η3-Propargyl Rhenium Complexes and Direct Observation of an Equilibrium between η3-Propargyl Rhenium Complexes and Rhenacyclobutenes

“…A similar DFT study of [(PH 3 ) 2 Pd(η 3 -CH 3 CHCCH)] + was performed by Delbecq, Sinou, and co-workers . Similar to the results reported here for a rhenium cation, they found that the central propargylic carbon was most positive, that the LUMO had a node at the central carbon, and that nucleophilic attack at the central carbon involved interaction with LUMO+1.…”

“…A similar DFT study of [(PH 3 ) 2 Pd(η 3 -CH 3 CHCtCH)] + was performed by Delbecq, Sinou, and co-workers. 37 Similar to the results reported here for a rhenium cation, they found that the central propargylic carbon was most positive, that the LUMO had a node at the central carbon, and that nucleophilic attack at the central carbon involved interaction with LUMO+1. Their conclusion that regioselective attack at the central carbon resulted from a combination of charge control and the availability of a low-lying orbital centered on the middle propargylic carbon is similar to that reported here.…”

Ring-Construction/Stereoselective Functionalization Cascade: Total Synthesis of Pachastrissamine (Jaspine B) through Palladium-Catalyzed Bis-cyclization of Propargyl Chlorides and Carbonates

“…Initially, regio- and stereoselective S N 2′ attack of palladium(0) to propargylic compounds proceeds to yield the allenylpalladium intermediate A . First cyclization by the hydroxy group on the central carbon of π-propargylpalladium complex B , which is formed by rearrangement of A , would generate a fused palladacyclobutene intermediate C . This is followed by protonation to form complex D without loss of chirality.…”

Synthesis of 2,3-Dihydro-2-Ylidene-1,4-Benzodioxins

“…This heteroannulation was extended to substituted catechols (Scheme 19) [45]. Methyl 1-methylpro-2-ynyl carbonate reacted with 3-methoxybenzene-1,2-diol to afford the two regioisomers 52a and 53a in a 1:1 ratio, while the condensation with 2,3-dihydroxybenzaldehyde or 3-nitrobenzene-1,2-diol gave a unique regioisomer 52b and 52c in 96 and 85% yields.…”