posted on 2015-10-02, 00:00authored byGuisheng Deng, Feng Wang, Shengle Lu, Bo Cheng
The construct of the core of pyrano[3,2-c]pyrazol-7(1H)-one derivatives is realized.
The key step includes a
tandem cyclization, namely, a metal-free cascade 6-π electrocyclic
ring closure-Michael reaction of 2-diazo-3,5-dioxo-6-ynoates (ynones).
The cascade reaction cleanly generated the desired products in excellent
yields under mild conditions.