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。
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。
According to four different methods, various types of N-acylpyrazoles were prepared from the corresponding pyrazoles and carboxylic acids or their acid chlorides. Although N-acylpyrazoles were inert to alcohols under neutral or weakly basic conditions, the alcoholysis was dramatically accelerated by the action of strong acid or base. On the basis of these chemical properties, the regioselective synthesis of methyl benzyl 2,2-dimethylglutarate was achieved by selective protection and functionalization of a carboxylic acid derivative using N-acylpyrazoles.
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
Diastereoselective .alpha.-Alkylation of 2-Acyl-3-phenyl-l-menthopyrazoles
作者:Choji Kashima、Iwao Fukuchi、Akira Hosomi
DOI:10.1021/jo00104a045
日期:1994.12
N-Acylpyrazoles were alpha-alkylated in good yields by the treatment with alkyl halides after metalation with LDA or LiHMDS, In the case of chiral N-acylpyrazoles, e.g., 2-acyl-3-phenyl-l-menthopyrazoles (4), the alpha-alkylation was highly diastereoselective. The subsequent alpha-alkylation products could be converted into esters in good yield in the presence of BF3.OEt(2) without the loss of the optical purity.
Kashima, Choji; Takahashi, Katsumi; Fukusaka, Kiyoshi, Journal of Heterocyclic Chemistry, 1995, vol. 32, # 6, p. 1775 - 1778
The aldol reaction of 1-acyl-3,5-dimethylpyrazoles (1) was kinetically controlled with syn stereoselectivity through lithium enolate intermediate using LDA. On the contrary, the anti stereoselective aldol reaction of 1 was caused by the action of DIEA in the presence of MgBr2 under the thermodynamic control. in the formation of syn-aldol products using 3-phenyl-1-menthopyrazole as a chiral auxiliary, the diastereoselectivity was observed up to 81% de with the predominant configuration of 2'S form.