Synthesis of functionalized tetrahydro-dispiro[pyrazolone 4, 2′-pyran-5′, 4″-pyrazolone] scaffolds via an Oxa-Michael-initiated cascade [4 + 2] annulation reaction using pyrazoledione-derived MBH-alcohols

In this study, an efficient protocol was developed for synthesizing tetrahydro-dispiro[pyrazolone 4, 2′-pyran-5′, 4″-pyrazolone] scaffolds, using pyrazoledione-derived MBH alcohols and arylidene pyrazolones. The reaction proceeds through an oxa-Michael-initiated cascade [4 + 2] annulation under metal-free conditions, affording a range of novel tetrahydrodispiro[pyrazolone-pyran-pyrazolone] derivatives with yields between 50 and 89 % and diastereoselectivities from 2.5:1 to >20:1. As a novel oxa-Michael donors, pyrazoledione-derived MBH alcohols were employed for the first time as a key substrate in this annulation reaction.