- Formal [4+2] cycloaddition of di-tert-butyl 2-ethoxycyclobutane-1,1-dicarboxylate with ketones or aldehydes and tandem lactonization.
Formal [4+2] cycloaddition of di-tert-butyl 2-ethoxycyclobutane-1,1-dicarboxylate with ketones or aldehydes and tandem lactonization.
Chemical & pharmaceutical bulletin (2012-01-10)
Ryohei Okado, Aya Nowaki, Jun-Ichi Matsuo, Hiroyuki Ishibashi
PMID22223370
ABSTRACT
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.
MATERIALS
Product Number
Brand
Product Description
Sigma-Aldrich
Tin(II) chloride dihydrate, puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., ≥98%