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Paper | Special issue | Vol 99, No. 1, 2019, pp.363-378
Published online, 14th September, 2018
DOI: 10.3987/COM-18-S(F)29
Synthesis of γ-Difluoromethylated Tetronate Derivatives from Squarates Using Difluoromethylphosphonate

Yoshihiko Yamamoto,* Yuki Ishida, Takashi Kurohara, Masatoshi Shibuya, and Takeshi Yasui

*Department of Basic Medicinal Sciences, Graduate School of Pharmaceutical Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan

Abstract

A new method for the synthesis of γ-difluoromethylated tetronates was developed using diethyl difluoromethylphosphonate as a difluoromethyl (CF2H) surrogate. The addition of a lithiated difluoromethylphosphonate to (semi)squarates at –90 °C afforded 4-hydroxycyclobutenones, which were converted into the corresponding tetronates by oxidative ring expansion using Pb(OAc)4. The final dephosphorylation was performed in MeOH using Cs2CO3 as the base, affording the desired γ-difluoromethyltetronates.