A theoretical study on the origin of π-facial stereoselectivity in the alkylation of enolates derived from 4-substituted γ-butyrolactones
A theoretical study on the origin of π-facial stereoselectivity in the alkylation of enolates derived from 4-substituted γ-butyrolactones
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DOI：
10.1021/ja044995n
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发表时间：
2005-03-23
影响因子：
15
通讯作者：
Ando, K
中科院分区：
文献类型：
--
作者：
Ando, K
在B3 LYP/6-31+G* 水平上研究了4-甲氧基甲基-γ-丁内酯烯醇化物与氯甲烷的烷基化反应。对游离烯醇化物进行构象搜索，得到了15种独特的构象，其构象范围在5.39 kcal/mol以内。定位了氯甲烷对这15种构象的反式和顺式攻击的过渡结构。在所有情况下，反跃迁结构比相应的同跃迁结构更稳定。在MP2、B3 LYP和HF水平上，采用6-31 +G* 基组，研究了Li+和二甲醚分子存在下γ-戊内酯的烷基化反应.在一种情况下，还通过将MP2结果与6-31 +G*、6-31 +G** 和6-311 +G** 基组进行比较来检验基组效应。研究表明，4-取代γ-丁内酯反选择性的主要来源是顺式过渡结构中的重叠应变。
The alkylation of 4-methoxymethyl-γ-butyrolactone enolate with methyl chloride was studied at the B3LYP/6-31+G* level. Conformer search of the free enolate gave 15 unique conformers within 5.39 kcal/mol. The transition structures for both anti- and syn-attacks of methyl chloride on these 15 conformers were located. In all cases, the anti-transition structures are more stable than the corresponding syn-ones. The alkylation of γ-valerolactone was studied at the MP2, B3LYP, and HF levels of theory with the 6-31 +G* basis set in the presence of Li+ and dimethyl ether molecules. Basis set effects were also examined by the comparison of the MP2 results with the 6-31 +G*, 6-31 +G**, and 6-311 +G** basis sets in one case. This study shows that the main source of the anti-selectivity of 4-substituted γ-butyrolactones is eclipsing strain in the syn-transition structures.