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
The hetero Diels-Alder reaction of 1-amino-3-siloxy-1,3-butadiene with a range of unactivated carbonyl compounds and imines proceeds in good yields readily under remarkably mild conditions at room temperature and in the absence of Lewis acid catalysts. The cycloadducts can be converted directly to the corresponding dihydro-4-pyrones and dihydro-4-pyridones.
Y. Huang, V. H. Rawal, Org. Lett., 2000, 2, 3321-3323.
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.