Metal- free and benign approach for the synthesis of dihydro-5' H- spiro[ benzo[ c] chromene8,4'- oxazole]-5', 6(7H)- dione scaffolds as masked amino acids plus circle plus
by Shafiee, B.; Duffield, J.; Timm, R.; Liyanage, R.; Lay, J. O.; Khosropour, A. R.; Rudbari, H. A.; Beyzavi, M. H.
An eco-friendly, straightforward, and three-component condensation/cascade reaction of 4-hydroxycoumarins and (Z)-azlactones to construct diversified dihydro-5H-spiro[benzo[c]chromene-8,4-oxazole]-5,6(7H)-diones as new masked amino acid derivatives has been developed with high to excellent yields and regio- and diastereoselectivity. This metal-free reaction proceeds via a one-pot cascade Michael addition/lactonization/decarboxylation reaction utilizing reusable propylene carbonate as a green solvent. The scale-up examination was also performed, showing high atom economy under the reaction conditions. Moreover, the mechanism of the reaction was further investigated using isotope-labeling, LC-MS monitoring, and TLC-MALDI-MS.
- Journal
- Green Chemistry
- Volume
- 21
- Issue
- 10
- Year
- 2019
- Start Page
- 2656-2661
- URL
- https://dx.doi.org/10.1039/c9gc00428a
- ISBN/ISSN
- 1463-9270; 1463-9262
- DOI
- 10.1039/c9gc00428a