Catalytic Asymmetric Synthesis of 3‑Hydroxy-3-trifluoromethyl Benzofuranones via Tandem Friedel–Crafts/Lactonization Reaction

A highly enantioselective and regioselective chiral Lewis acid catalyzed tandem Friedel–Crafts/lactonization reaction is reported, providing direct access to plenty of 3-hydroxy-3-trifluoromethyl benzofuran-2-ones in up to 94% yields with up to >99% ee. Mechanistic study reveals that the interactions between the phenolic hydroxyl group and trifluoropyruvate are the most likely contributing factor to the high enantio- and regioselectivity. Optically pure (−)-BHFF can be obtained in gram-scale with 0.05 mol % catalyst, demonstrating the potentially utility of this method in medicinal chemistry

ANOVAs for the effects of treatment (removing or retaining understory vegetation and litter), species and plant tissue on the concentration of nitrogen ([N]), phosphorus ([P]), and N∶P ratio at the two plantations.

<p><i>F</i>-ratios and significance values for treatment, species, plant tissue and their interactions are given (significant results in <i>bold</i>).</p

Relationship between RGR of height and leaf [N], [P] and N∶P ratio for the transplanted <i>C. chinensis</i>, <i>M. chapensis</i>, and <i>P. rubra</i> seedlings.

<p>Relationship between RGR of height and leaf [N], [P] and N∶P ratio for the transplanted <i>C. chinensis</i>, <i>M. chapensis</i>, and <i>P. rubra</i> seedlings.</p

Relative growth rate (RGR) of height for transplanted <i>C. chinensis</i>, <i>M. chapensis</i>, and <i>P. rubra</i> seedlings affected by removing (VR) or retaining (CK) understory vegetation and litter at the two plantations.

<p>EP: <i>Eucalyptus</i> plantation; NP: native species plantation.</p

The dominant understory species and its coverage, standing litter biomass, soil properties, and light penetration at the two plantations.

<p>Values are means ± standard errors and are based on data collected just before the experiment began and from plots where vegetation and litter were not removed.</p><p>Means in a column followed by different letters are significantly different (<i>p</i><0.05) according to t-test. EP, <i>Eucalyptus</i> plantation; NP, Native species plantation.</p

Concentration of nitrogen ([N]), phosphorus ([P]), and N:P ratio in the leaves, stems and roots of <i>C. chinensis</i>, <i>M. chapensis</i> and <i>P. rubra</i> seedlings treated with removal (VR) or retention (CK) of understory vegetation and litter at the two plantations.

<p>Concentration of nitrogen ([N]), phosphorus ([P]), and N:P ratio in the leaves, stems and roots of <i>C. chinensis</i>, <i>M. chapensis</i> and <i>P. rubra</i> seedlings treated with removal (VR) or retention (CK) of understory vegetation and litter at the two plantations.</p

Relationships between scaling constant/intercept and tree age (a), diameter at breast height (DBH, b), height (c), density (d), latitude (e), longitude (f), and elevation (g).

<p>The model with the best fit among the linear, quadratic and power function models is presented. ** significant at α = 0.01 level. Error bars are standard errors of the scaling exponents.</p

Relationships between scaling exponent and tree age (a), diameter at breast height (DBH, b), height (c), density (d), latitude (e), longitude (f), and elevation (g).

<p>The scaling exponent of each age, DBH, height, density, latitude, longitude, and elevated group was estimated using reduce major axis (RMA) regression analysis. The model with the best fit among the linear, quadratic and power function models is presented. ** significant at α = 0.01 level. Error bars are standard errors of the slopes.</p

Relationships between belowground biomass and tree age (a), diameter at breast height (DBH, b), height (c), density (d), latitude (e), longitude (f), and elevation (g).

<p>The model with the best fit among the linear, quadratic and power function models is presented. ** significant at α = 0.01 level. Error bars are too small to be shown.</p

Highly Enantioselective Nickel-Catalyzed Oxa-[3+3]-annulation of Phenols with Benzylidene Pyruvates for Chiral Chromans

Nickel-catalyzed asymmetric annulation of oxygenated phenols and previously challenging 3-aminophenols with β,γ-unsaturated α-ketoesters is described, leading to rapid access to a variety of oxygenated and 7-aminated chromans in excellent yields with excellent diastereoselectivities and enantioselectivities under mild conditions. This method was readily scaled-up to gram scale and applied for a concise synthesis of two potential anticancer agents 7-aminated 4-arylchromans