Okado Ryohei, Nowaki Aya, Matsuo Jun-Ichi, Ishibashi Hiroyuki
School of Pharmaceutical Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
Chem Pharm Bull (Tokyo). 2012;60(1):21-2. doi: 10.1248/cpb.60.21.
A catalytic 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.
催化量的四氯化锡催化2-乙氧基环丁烷-1,1-二羧酸二叔丁酯与酮或醛进行形式上的[4+2]环加成反应，生成6-乙氧基二氢-2H-吡喃-3,3(4H)-二羧酸二乙酯，而两当量的三氟甲磺酸三甲基硅酯则促进串联[4+2]环加成和内酯化反应，得到3-氧代-2,6-二氧杂双环[2.2.2]辛烷-4-羧酸酯。
