L-(+)-α-Bromobenzeneacetic Acid (−)-Menthyl Ester

Kolev, Tsonko; Preut, H.; Koniczek, L.; Bleckmann, P.; Juchnovski, I.; Mladenova, M.

doi:10.1107/s0108270195001430

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“…虽然可以想办法将该外消旋体拆开得到旋光的分子, 但根据过渡金属催化的 ATRP 引发机理 [18] (见 Scheme 1), 该分子由于其手性碳是直接与溴原子相连, 在碳溴键断裂后形成的自由基就消旋化, 因此在引发过程中失去了手性诱导作用. [22,23] , C 的合成也有文献报道 [24,25] , 我们按文献报道的方法合成 A, B 和 C. D 和 E 未见文献报道. 我们先用氯化亚砜将 α-溴代苯乙酸转变成 α-溴代苯乙酰氯, 然后再分别与相应的醇或胺反应即得相应的酯或酰胺, 反应路线如 Scheme 2 所示.…”

Section: 结果与讨论unclassified

Synthesis of Several Chiral Atom Transfer Radical Polymerization Initiators and Its Helix-sense-selective Initiating Function for ATRP

Wang¹,

Yang²,

Yang³

et al. 2012

Acta Chim. Sinica

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Five optically active alkyl bromides were synthesized and were used as chiral atom transfer radical polymerization (ATRP) initiators for the helically selective polymerization of 1-phenyldibenzosuberyl methacrylate (PDBSMA). In order to avoid the racemization of the primary free radical formed in initiating step, the optically active alkyl bromide initiators were designed as such a structure in which the bromine atom did not connect to the chiral center. The chiral ATRP initiators tested here are (S)-2,2'-di(bromomethyl)-1,1'-binaphthyl, (S)-2-bromomethyl-2-methyl-1,1'-binaphthyl, menthyl α-bromophenylacetate, N-menthyl α-bromophenylacetamide and (3β,5α)-cholestan-3-yl α-bromo phenylacetate. (S)-2,2'-Di(bromomethyl)-1,1'-binaphthyl, (S)-2-bromomethyl-2-methyl-1,1'-binaphthyl and menthyl α-bromophenylacetate were synthesized following the method reported by literatures. N-menthyl α-bromophenylacetamide was synthesized by adding dropwise the solution of α-bromophenylacetyl chloride in tetrahydrofuran (THF) into the mixture of menthylamine, triethylamine and THF with stirring at room temperature within 3 h and stirring at room temperature for another 8 h after the addition. (3β,5α)-Cholestan-3-yl α-bromo phenylacetate was synthesized using the method for the synthesis of menthyl α-bromophenylacetate except using (3β,5α)-cholestanol instead of menthol. The poly-PDBSMA obtained from the ATRP initiated by the optically active alkyl bromides was fractionated into THF-soluble part and THF-insoluble part. THF-soluble part was optically active. By studying the chiroptical properties of the THF-soluble part of the poly-PDBSMA and by comparing the optical rotation of the THF-soluble part of the poly-PDBSMA with that of the poly(methyl methacrylate) (poly-MMA) obtained under the same polymerization condition, we concluded that the ATRP initiated by the optically active alkyl bromides was helix-sense selective. The NMR study of poly-MMA derived from the THF-insoluble part showed that the polymer produced from the polymerization initiated by (S)-2,2'-di(bromomethyl)-1,1'-binaphthyl was isotactic, which proved further that the ATRP initiated by the optically alkyl bromines was helix-sense selective. Among the five optically active alkyl bromides, (S)-2,2'-di(bromomethyl)-1,1'-binaphthyl and (S)-2-bromomethyl-2-methyl-1,1'-binaphthyl had the best helical selectivity. The helix-sense selectivity depended on the polymerization temperature. The ceiling temperature is 70 ℃. In the range of 0-70 ℃, the helix-sense selectivity increased with the increase of the polymerization temperature.

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