The SN2 Reactivity of 3,3-Disubstituted 1,2-Dioxetanes with Morpholine
摘要:
The reaction of morpholine with the 3-aryl-3-methyldioxetanes 1a-c (Y = 4-OMe, H, 4-NO2), the 3-(methoxymethyl)-3-phenyldioxetane (1d), and the 3-(halomethyl) 3-phenyldioxetanes 1e,f (X = Cl, Br) was investigated to determine the S(N)2 reactivity of these dioxetanes and the product distribution of the hydroxylamine ether 2 adducts and the dioxetane fragmentation products 3. It was shown that the overall rectivity and the product distribution are strongly dependent on the substituents of the dioxetanes 1. Thus, the reactivity of the dioxetanes 1 toward morpholine was demonstrated to correlate with the electron-accepting propensity of the substituents in the 3-position, while the product distribution depends on the electronic features of the primary dipolar adduct, which results from nucleophilic attack at the dioxetane peroxide bond. Electron-donating substituents (Y = 4-OMe) favor proton transfer from the hydroxylammonium site to the alkoxide ion due to the enhanced basicity of the latter, and, therefore, the formation of the hydroxylamine ether 2 is promoted. Additionally, electron-accepting substituents (Y = NO2) facilitate the Grob fragmentation of the primary dipolar adduct to the dioxetane cleavage products 3. The unexpected formation of the hydroperoxide 4f in the reaction of the dioxetane If with morpholine was shown to result from acid-catalyzed ring opening of the dioxetane by morpholinium bromide and subsequent morpholine trapping of the resulting stabilized, bromine-bridged benzylic cation.
Reaction of 1,2-dioxetanes with heteroatom nucleophiles: adduct formation by nucleophilic attack at the peroxide bond
作者:Waldemar Adam、Markus Heil
DOI:10.1021/ja00040a017
日期:1992.7
The reactions of 3,3-disubstituted 1,2-dioxetanes 1 with numerous heteroatom nucleophiles, e.g., R 2 NH, R 3 N, RSH R 2 S, CN - , SCN - , Br - , Cl - , OH - , and O 2 .- , were investigated. Initial nucleophilic substitution at the sterically less hindered site of the dioxetane peroxide bond leads to addition, deoxygenation, and fragementation products. The observed S N 2 chemistry was substantiated
3,3-二取代的 1,2-二氧杂环丁烷 1 与许多杂原子亲核试剂的反应,例如 R 2 NH、R 3 N、RSH R 2 S、CN - 、SCN - 、Br - 、Cl - 、OH - 和O 2 .- ,进行了调查。在二氧杂环丁烷过氧化物键的空间位阻较小的位点处的初始亲核取代导致加成、脱氧和断裂产物。观察到的 SN 2 化学反应得到二氧杂环丁烷 1c 的证实,因为溴离子被邻近的醇盐离子位点置换得到环氧化物产物