Synthesis of New 3,4-Disubstituted 2,5-Dihydro-1<i>H</i>-pyrrol-1-yloxyl Spin-Label Reagents via Allylic Rearrangements
作者:Kálmán Hideg、Cecília P. Sár、Olga H. Hankovszky、Tünde Tamás、Gyula Jerkovich
DOI:10.1055/s-1993-25870
日期:——
Several 3,4-disubstituted 2,5-dihydro-1H-pyrrol-1-yloxyl radicals were synthesized. 2,5-Dihydro-3-hydroxymethyl-2,2,5,5-tetramethyl-1H-pyrrol-1-yloxyl radical (1) was reacted with triethyl orthoacetate in a Claisen rearrangement to give the exoolefinic compound 2. This was converted to its 1-acetoxyl derivative 3, which was then brominated in the allylic position. Subsequent rearrangement gave the endoolefinic compound 1-acetoxyl-4-bromomethyl-3-ethoxycarbonylmethyl-2,2,5,5-tetramethyl-1H-pyrrole radical (4). The allylic bromine could be replaced with nucleophiles (NaSCN, KSeCN, thiourea, selenourea, NaN3 and KSSO2Me) to give 5a-e and 26. The diamagnetic thiocyanates and selenocyanates could be reduced with sodium borohydride to the free thiol and selenol monoradicals, which were oxidized to reversible, ester-functionalized disulfide or diselenide diradical reagents 24 and 25.
合成了几个3,4-二取代的2,5-二氢-1H-吡咯-1-氧基自由基。2,5-二氢-3-羟甲基-2,2,5,5-四甲基-1H-吡咯-1-氧基自由基(1)经Claisen重排反应与三乙基原乙酸酯反应,得到外烯烃化合物2。将其转化为1-乙酸氧基衍生物3,然后在烯丙位进行溴化。随后的重排反应得到内烯烃化合物1-乙酸氧基-4-溴甲基-3-乙氧羰甲基-2,2,5,5-四甲基-1H-吡咯自由基(4)。烯丙位的溴可以被亲核试剂(NaSCN、KSeCN、硫脲、硒脲、NaN3和KSSO2Me)取代,得到5a-e和26。无磁性的硫氰酸盐和硒氰酸盐可以用硼氢化钠还原成自由的硫醇和硒醇单自由基,这些自由基被氧化成可逆的、酯功能化的二硫化物或二硒化物双自由基试剂24和25。