Formal [4+2] Cycloaddition of di-tert-Butyl 2-Ethoxycyclobutane-1,1-dicarboxylate with Ketones or Aldehydes and Tandem Lactonization
作者:Ryohei Okado、Aya Nowaki、Jun-ichi Matsuo、Hiroyuki Ishibashi
DOI:10.1248/cpb.60.21
日期:——
amount of tin(IV) chloride catalyzed formal [4+2] cycloaddition reaction of di-tert-butyl 2-ethoxycyclobutane-1,1-carboxylate with ketones or aldehydes to give diethyl 6-ethoxydihydro-2H-pyran-3,3(4H)-dicarboxylates, whereas two equivalents of trimethylsilyl triflate promoted tandem [4+2] cycloaddition and lactonization to afford 3-oxo-2,6-dioxabicyclo[2.2.2]octane-4-carboxylate esters.
催化量的氯化锡(IV)催化2-乙氧基环丁烷-1,1-羧酸二叔丁酯与酮或醛的正式[4 + 2]环加成反应,得到6-乙基乙氧基二氢-2H-吡喃-3, 3(4H)-二羧酸酯,而三当量的三甲基甲硅烷基三氟甲磺酸酯可促进串联[4 + 2]环加成和内酯化,从而提供3-oxo-2,6-dioxabicyclocyclo [2.2.2]辛烷-4-羧酸酯。