95060-73-4Relevant academic research and scientific papers
Theory-guided design of Br?nsted acid-assisted phosphine catalysis: synthesis of dihydropyrones from aldehydes and allenoates
Creech, Gardner S.,Zhu, Xue-Feng,Fonovic, Branden,Dudding, Travis,Kwon, Ohyun
, p. 6935 - 6942 (2008/09/21)
The phosphine-catalyzed addition of 2,3-butadienoates to aldehydes has been extended to the formation of disubstituted dihydro-2-pyrones. The requisite shift in equilibrium of the intermediate zwitterionic β-phosphonium dienolates toward the s-cis intermediate was accomplished through the use of a Br?nsted acid additive, which disrupts the favorable Coulombic interaction present in the s-trans intermediate. The detailed nature of the synergistic interactions involving the Br?nsted acid additives and phosphine involved in the formation of s-cis β-phosphonium dienolates was analyzed through a series of DFT calculations. Unlike previously reported annulations of aldehydes with allenoates, where trialkylphosphines are optimal catalysts, in this study triphenylphosphine was also found for the first time to be a suitable catalyst for the synthesis of dihydropyrones. This method provides a one-step route toward functionalized dihydropyrones from simple, stable starting materials. In addition, new reaction pathways of phosphine-catalyzed allene annulations are unveiled, with the formation of dihydropyrones being the first example of dual activation in this sphere.
Alcohol-assisted phosphine catalysis: One-step syntheses of dihydropyrones from aldehydes and allenoates
Creech, Gardner S.,Kwon, Ohyun
, p. 429 - 432 (2008/09/19)
This paper describes the phosphine-catalyzed annulation of methyl allenoate with various aromatic aldehydes to form 6-aryl-4-methoxy-5,6dihydro-2-pyrones. In this reaction, the addition of an alcohol was necessary to induce dihydropyrone formation, with the optimal agent being methanol. Moreover, the addition of n-butyllithium suppressed the formation of the noncyclized product, leading to the exclusive isolation of the dihydropyrone. This method provides an efficient, one-step route toward disubstituted dihydropyrones from simple, stable starting materials.
Reaction of Ethyl χ-Bromo-β-methoxycrotonate with Carbonyl Compounds. Synthesis of 4-methoxy-6-substituted-5,6-dihydro-2H-pyran-2-ones and 3-Substituted 3-Pyrazolin-5-ones
Shandala, Mowafak Y.,Ayoub, Mikdad T.,Mohammad, Mouyayed J.
, p. 1755 - 1756 (2007/10/02)
Ethyl β-methoxycrotonate I reacts with substituted carbonyl compounds II in benzene to give 4-methoxy-6-substituted-5,6-dihydro-2H-pyran-2-ones III.The reaction of IIIa and j with hydrazine hydrate in ethanol leads to 3--5-hy
