Chiral Brønsted Acid-Catalyzed Asymmetric Allyl(propargyl)boration Reaction of ortho-Alkynyl Benzaldehydes: Synthetic Applications and Factors Governing the Enantioselectivity
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- 作者：Elsa Rodríguez ; Matthew N. Grayson ; Amparo Asensio ; Pablo Barrio ; K. N. Houk ; Santos Fustero
- 刊名：ACS Catalysis
- 出版年：2016
- 出版时间：April 1, 2016
- 年：2016
- 卷：6
- 期：4
- 页码：2506-2514
- 全文大小：604K
- ISSN：2155-5435
文摘
Chiral Brønsted acid-catalyzed allyl(propargyl)boration of ortho-alkynyl benzaldehydes gives rise to ω-alkynyl homoallylic(homopropargylic)alcohols that can be further transformed to complex molecular scaffolds via subsequent hydroalkoxylation, ring-closing enyne metathesis (RCEYM), or intramolecular Pauson–Khand reaction (PKR). Optimizations of each two-step transformation is reported. A strong dependence between enantioselectivities and the nature of the substitution at the alkynyl moiety is observed, showcasing that the triple bond is not merely a spectator in this transformation. Density functional theory (DFT) calculations (M06-2X/6-311+G(d,p)–IEFPCM//B3LYP/6-31G(d)) show that this dependence is the result of the steric and electronic properties of the alkyne substituent.