α-Carbonyl Substituent Effect on the Lifetimes of Triplet 1,4-Biradicals from Norrish-Type-II Reactions
作者:Xichen Cai、Peter Cygon、Bernd Goldfuss、Axel G. Griesbeck、Heike Heckroth、Mamoru Fujitsuka、Tetsuro Majima
DOI:10.1002/chem.200600011
日期:2006.6.2
Norrish-Type-II hydrogen transfer from alpha-heteroatom-substituted beta-branched butyrophenones 1-6 and detected by laser flash absorption measurements. For three oxy-substituted compounds 2-4 (R(alpha)=OH, OCOMe, OCOOEt) comparable lifetimes were determined in acetonitrile (roughly 1.5 micros). In benzene, divergent trends were observed: for the hydroxy compound 2 a lower lifetime of 790 ns was determined
三重态1,4-双自由基是由Norrish-Type-II氢从α-杂原子取代的β-支化丁苯酮1-6转移生成的,并通过激光闪光吸收测量进行检测。对于三种氧基取代的化合物2-4(Rα= OH,OCOMe,OCOOEt),在乙腈中(约1.5微米)确定了相当的寿命。在苯中,观察到了不同的趋势:对于羟基化合物2,确定了较低的寿命790 ns,而对于3和4,则将其寿命提高至4.9微米。α-氨基取代的化合物1和6的光解会导致具有明显较低寿命的瞬态物质(在苯中为1 160 ns,在乙腈中为450 ns;在两种溶剂中为6 <100 ns)。甲氧基氧基底物5在光解时经历快速的CO键裂解,并且未检测到瞬态三重态物质。