Synthesis of 2,3-dihydro-4H-pyran-4-ones
A metal-free, pTsOH-catalyzed intramolecular rearrangement of δ-hydroxyalkynones provides substituted 2,3-dihydro-4H-pyran-4-ones. The rearrangement occurs with high regioselectivity under mild conditions.
S. P. Gholap, D. Jangid, R. A. Fernandes, J. Org. Chem., 2019, 84, 3537-3551.
A BINOLate-zinc complex prepared in situ from Et2Zn and 3,3'-dibromo-BINOL is an efficient catalyst for the enantioselective hetero-Diels-Alder reaction of Danishefsky's diene with aldehydes to give 2-substituted 2,3-dihydro-4H-pyran-4-ones in up to quantitative yield and 98% ee.
H. Du, J. Long, J. Hu, X. Li, K. Ding, Org. Lett., 2002, 4, 4349-4352.
A new type of chromium-salen complex bearing DIANANE (endo,endo-2,5-diaminonorbornane) has been applied to the hetero-Diels-Alder reaction of Danishefskys diene with various aldehydes. The reactions afford the corresponding 2-substituted 2,3-dihydro-4H-pyran-4-ones in high yields and enantioselectivities.
A. Berkessel, N. Vogl, Eur. J. Org. Chem., 2006, 5029-5035.