A general, regioselective synthesis of substituted benzocyclobutenedione monoacetals
摘要:
A general, regioselective synthesis of substituted benzocyclobutenedione monoacetals is reported. Palladium-catalyzed coupling of a variety of 4-chlorocyclobutenones with 3-(tri-n-butylstannyl)-3-cyclobutene-1,2-dione 2-(ethylene acetal) and heating up to 70-100-degrees-C produces substituted benzocyclobutenedione monoacetals in good to excellent yields. Thia chemistry is presumed to proceed through palladium-catalyzed formation of a 3-(1-oxo-2-cyclobuten-4-yl)-3-cyclobutene-1,2-dione-2-(ethylene acetal) followed by a thermally induced ring opening to a dienyl ketene and subsequent six-electron electrocyclic ring closure and tautomerization. 2,3-Disubstituted 4-chlorocyclobutenones afford palladium intermediates which couple exclusively at the least-substituted allylic terminus. 2,3,4-Trisubstituted 4-chlorocyclobutenones have not been studied in detail; however, preliminary results suggest that regioselective allylic cross-coupling can be achieved. The methodology described provides an expedient and efficient route to previously difficult-to-prepare benzocyclobutenedione derivatives. These function as important synthetic intermediates in a variety of reactions developed in these and other laboratories.
Synthesis of alkyl substituted cyclobutenediones by free radical chemistry. Carbon for nitrogen replacement in the α-Amino acid Bioisostere -- 34-Diamino-3-cyclobutene-1,2-dione.
作者:William A. Kinney
DOI:10.1016/s0040-4039(00)73543-x
日期:1993.4
A novel free radical method for the synthesis of alkyl substituted cyclobutenediones was demonstrated, allowing for incorporation of a variety of functionalities. The synthesis of an analog of NMDA antagonist 1 was thereby facilitated.
An expedient approach to synthesize fluorescent 3-substituted 4H-quinolizin-4-ones via (η<sup>4</sup>-vinylketene)-Fe(CO)<sub>3</sub> complexes
作者:Alfredo Rosas-Sánchez、Rubén A. Toscano、José G. López-Cortés、M. Carmen Ortega-Alfaro
DOI:10.1039/c4dt03021d
日期:——
From simple starting materials, an efficient methodology for the synthesis of 3-substituted 4H-quinolizin-4-ones using (η4-vinylketene)-Fe(CO)3 complexes as key intermediates was developed. Fluorescent properties and quantum yields were determined.
TFA-catalyzed ring transformation of 4-hydroxycyclobutenone: A simple and general route for preparation of 3-substituted 4-aminofuran-2(5H )-ones †
作者:Jie Wang、Xin Jiang、Ming Chen、Zongming Ge、Yuefei Hu、Hongwen Hu
DOI:10.1039/b004654j
日期:——
positions, respectively, to yield 4-substituted 3-aminocyclobutene-1,2-diones 14. Reduction of compounds 14 with NaBH4 yield 2-substituted 3-amino-4-hydroxycyclobutenones 15 in high yields. By ring transformation of products 15 catalyzed by TFA, a simple and generalroute for the preparation of 3-substituted 4-aminofuran-2(5H)-ones 4 is developed. A two-step mechanism is proposed to describe the ring
Highly Regioselective Monothionation of Squaric and Semisquaric Acid Derivatives
作者:Martin Müller、Matthew J. Heileman、Harold W. Moore、Ernst Schaumann、Gunadi Adiwidjaja
DOI:10.1055/s-1997-1496
日期:1997.1
An efficient synthesis of 4-thioxocyclobut-2-enones by the action of 0.5 molar equivalents of Lawesson’s reagent on the corresponding diones is reported.
Nickel-catalyzed ring-opening of α-hydroxycyclobutenones with a remarkable ligand effect
作者:Songsong Gao、Xiangdong Hu
DOI:10.1039/c7cc03340k
日期:——
A Ni-catalyzed ring-opening of α-hydroxycyclobutenones is reported herein. A remarkable ligand effect was observed during transformations following the ring-opening. The employment of PPh3 leads to the formation of 2-furanones 2 through a migration of an alkoxyl group, and 2-furanones 3 were generated through a migration of hydrogen in the presence of Xantphos, affording a divergent approach to 2-furanones