AbstractThe palladium‐catalyzed synthesis of dihydroisobenzofurans has been performed by sequential Sonogashira cross‐coupling/cyclization reactions between terminal alkynes and 2‐(hydroxymethyl)bromo‐ and chlorobenzenes in methanol as solvent at 130 °C under microwave irradiation. A 4,4′‐dichlorobenzophenone oxime‐derived chloro‐bridged palladacycle is an efficient pre‐catalyst to perform this tandem process using 2‐dicyclohexylphosphanyl‐2′,4′,6′‐triisopropylbiphenyl (Xphos) as ancillary ligand and potassium hydroxide as base in the absence of a copper cocatalyst. Under these conditions, functionalized 2‐bromo‐ and 2‐chlorobenzaldehydes are also suitable partners in the domino process affording phthalans in good yields. All the reactions can be performed under air and employing reagent‐grade chemicals under low loading conditions (1 mol% Pd).magnified image
nucleophilic addition/annulation reaction of ortho-alkynylbenzaldehydes in the presence of methanol. The reactions of aryl-, trimethylsilyl- and diethoxymethyl-substituted alkynylbenzaldehydes occurred with complete regioselectivity in good to excellent yields undermicrowaveirradiation. The reactions of alkyl-substituted alkynylbenzaldehydes took place with good yields and high regioselectivity only when
Solvent-Switched Benzylic Methylene Functionalization: Addition, Ring-Opening, Cyclization, and Unexpected Cleavage of C–O and C–C Bonds
作者:Deng Yuan Li、Xue Song Shang、Guo Rong Chen、Pei Nian Liu
DOI:10.1021/ol401470y
日期:2013.8.2
been achieved using imines as reagents and potassium tert-butoxide as the catalyst. Depending on the solvent used, the reaction proceeds by two pathways. In THF, an addition/elimination reaction of exo-cyclic enol ethers with imines provides dihydroisobenzofuranderivatives in good yield. In DMSO, an addition/ring-opening/cyclization cascade reaction occurs with unexpected cleavage of C–O and C–C bonds
Alkyl Isobenzofurans from Phthalides; Inter and Intramolecular Diels-Alder Reactions
作者:Sanath K. Meegalla、Russell Rodrigo
DOI:10.1055/s-1989-27438
日期:——
A general procedure for the conversion of phthalides 1 to alkyl isobenzofurans 4 is described and illustrated with nine. examples. Thus, the alkylidene phthalans 3 produced from the phthalides 1 in one step are in acid catalyzed equilibrium with the. alkyl isobenzofurans 4 which are trapped in situ by dienophiles as the inter- and intramolecular Diels-Alder adducts 5-9.
Regio- and stereoselective intramolecular hydroalkoxylation of aromatic alkynols: an access to dihydroisobenzofurans under transition-metal-free conditions
An efficient, transition-metal-free method to synthesize dihydroisobenzofuran derivatives via intramolecular hydroalkoxylation of aromatic alkynols with the promotion of cesium carbonate has been developed. The reaction proceeds regioselectively with exclusive formation of 5-exo-dig product, and only Z-isomer of the new generated double bond is observed. This new protocol features with milder reaction conditions, more convenient operation and satisfactory selectivities.