Competition between peroxy acid oxygens as hydrogen bond acceptors in B3LYP transition structures for epoxidations of allylic alcohols with peroxyformic acid
Competition between peroxy acid oxygens as hydrogen bond acceptors in B3LYP transition structures for epoxidations of allylic alcohols with peroxyformic acid
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DOI：
10.1021/jo981743u
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发表时间：
1999-05-28
影响因子：
3.6
通讯作者：
Rastelli, A
中科院分区：
文献类型：
--
作者：
Freccero, M;Gandolfi, R;Rastelli, A
利用B3LYP方法，利用6-31G*、6-311G**和6-311+G**三个基组，确定了8-丙烯-1-醇和2-环丁烯-1-醇与过氧甲酸环氧化反应的过渡结构。过氧酸对这些醇的同步攻击导致同步TSs，其中氢键是有效的。烯丙基羟基总是充当氢键的给体，羰基氧或过氧酸的过氧氧都可以充当氢键的受体。以丙烯醇为例，与参与氢键的过氧氧形成的两个同步TSs （O-C-C=C二面角分别为135.0°和16.0°）的自由焓与与羰基氧形成氢键的对应TSs （O-C-C=C二面角分别为134.0°和16.3°）的自由焓相当。基集扩展和静电溶剂化效应有利于前一种TSs。在环丁醇的情况下，与羰基氧参与氢键的TS （O-C-C=C二面角= 124.2°）比对应的TS （O-C-C=C二面角= 128.0°）要稳定得多（大于等于1.8 kcal/mol(-1)）。抗TSs本质上比合成TSs更不稳定，但这种差异在溶液中大大减少。结合计算数据，讨论了丙烯醇过氧酸环氧化反应的Sharpless定性TS模型。
The transition structures (TSs) for the epoxidation of 8-propen-1-ol and 2-cyclobuten-1-ol with peroxyformic acid have been located with the B3LYP method using three basis sets (i.e., 6-31G*, 6-311G**, and 6-311+G**). Syn attacks on these alcohols by peroxy acid lead to syn TSs in which hydrogen bonding is operative. The allylic OH group always acts as hydrogen-bond donor while either the carbonyl oxygen or the peroxo oxygens of the peroxy acid can play the role of hydrogen-bond accepters. In the case of propenol, the two syn TSs (O-C-C=C dihedral angles: 135.0 degrees and 16.0 degrees, respectively) with the peroxo oxygens involved in hydrogen bonding have free enthalpies comparable with those of their counterparts (O-C-C=C dihedral angles: 134.0 degrees and 16.3 degrees, respectively) with hydrogen bonding to carbonyl oxygen. Basis set extension as well as electrostatic solvation effects favor the former TSs over the latter ones. In the case of cyclobutenol the syn TS (O-C-C=C dihedral angle = 124.2 degrees) with hydrogen bonding to peroxo oxygens is significantly more stable (by greater than or equal to 1.8 kcal/mol(-1)) than the corresponding TS (O-C-C=C dihedral angle = 128.0 degrees) with carbonyl oxygen involved in hydrogen bonding. Anti TSs are inherently less stable than syn TSs but this difference is strongly reduced in solution. The Sharpless qualitative TS model for peroxy acid epoxidation of allyic alcohols is discussed in the light of computational data.