Catalytic enantioselective α‐fluorination reactions of carbonyl compounds are among the most powerful and efficient synthetic methods for constructing optically active α‐fluorinated carbonyl compounds. Nevertheless, α‐fluorination of α‐nonbranched carboxylic acid derivatives is still a big challenge because of relatively high pKa values of their α‐hydrogen atoms and difficulty of subsequent synthetic
羰基化合物的催化对映选择性α-氟化反应是构建光学活性α-氟化羰基化合物的最有效,最有效的合成方法之一。然而,由于α-非支链羧酸衍生物的α-氢原子的p K a值相对较高,并且随后不进行差向异构化就很难进行合成转化,因此α-非支链羧酸衍生物的α-氟化仍然是一个很大的挑战。本文显示了3-(2-萘基)-1-丙氨酸衍生的酰胺的手性铜(II)络合物是N-(α-芳基乙酰基)和N的对映体和定点α-氟化的高效催化剂-(α-烷基乙酰基)3,5-二甲基吡唑。转化的底物范围非常广泛(25个实例,其中包括季铵化α-氟化α-氨基酸衍生物)。α-氟化产物几乎没有差向异构化地转化为相应的酯,仲酰胺,叔酰胺,酮和醇。
Iodonium salts as efficient iodine(<scp>iii</scp>)-based noncovalent organocatalysts for Knorr-type reactions
作者:Sevilya N. Yunusova、Alexander S. Novikov、Natalia S. Soldatova、Mikhail A. Vovk、Dmitrii S. Bolotin
DOI:10.1039/d0ra09640g
日期:——
Hypervalent iodine(III)-derivatives display higher catalytic activity than other aliphatic and aromatic iodine(I)– or bromine(I)-containing substrates for a Knorr-type reaction of N-acetyl hydrazides with acetyl acetone to give N-acyl pyrazoles. The highest activity was observed for dibenziodolium triflate, for which 10 mol% resulted in the generation of N-acyl pyrazole from acyl hydrazide and acetyl
对于N-乙酰酰肼与乙酰丙酮的克诺尔型反应生成N-酰基吡唑,高价碘 ( III ) 衍生物比其他脂肪族和芳香族含碘 () 或溴 () 的底物表现出更高的催化活性。三氟甲磺酸二苯并碘鎓的活性最高,10 mol% 会导致酰肼和乙酰丙酮在 50 °C 下反应 3.5-6 小时,生成N-酰基吡唑,分离收率高达 99%。 1 H NMR滴定数据和DFT计算表明碘( III )的催化活性是由与酮的结合引起的。
Enantiomerically enriched preparation of enolizable β-keto amides. Diastereoselective α-acylation and subsequent aminolysis of 2-acyl-3-phenyl-l-menthopyrazoles
After deprotonation with LDA, 2-acyl-3-phenyl-l-menthopyrazoles (13) were diastereomerically α-acylated to give N-(3-phenyl-l-menthopyrazolyl) β-ketoamides (14–19). The subsequentamides were converted into the corresponding N-alkyl amides (21–24) retaining their enantiomericenrichment on the α-position. These are the first examples of enolizableβ-keto acid derivatives having only one chiral center
N-acyl pyrazoles were efficiently and selectively prepared through the 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD)-catalyzed reaction of nitrosoarenes with N-acyl pyrazoles via an N-nitroso aldol reaction/dehydration sequence. The α-imino acyl pyrazoles were demonstrated to be new versatile intermediates for practical one-pot syntheses of α-imino amides, dipeptide precursors, esters, and β-amino alcohols
Three-Component Asymmetric Mannich Reaction Catalyzed by a Lewis Acid with Rhodium-Centered Chirality
作者:Lihe Feng、Xuemei Dai、Eric Meggers、Lei Gong
DOI:10.1002/asia.201700189
日期:2017.5.4
A highly efficient directasymmetric three‐component Mannich reaction of an N‐acylpyrazole, an aldehyde and a primary or secondary amine, was enabled by a rhodium‐based Lewis‐acid catalyst with metal‐centered chirality. Excellent enantioselectivities were achieved for a variety of substrates at a typical catalyst loading of merely 0.5 mol % (23 examples, up to 98 % ee).