Cyclization and Ring-Expansion Processes Involving Samarium Diiodide Promoted Reductive Formation and Subsequent Oxidative Ring Opening of Cyclopropanol Derivatives
convert to cyclic conjugated enones in moderate to good yields. In addition, the reduction−oxidation reaction sequences can be successfully performed in one pot. The regioselectivities of cyclopropane ringopening in the bicyclic substrates depend on the oxidizing agents used. For example, reactions promoted by FeCl3 with pyridine lead to the expected ring-expansion process involving internal-bond cleavage
io二碘化物促进了各种α-溴甲基环烷酮的反应,然后用三甲基甲硅烷基氯进行处理,导致嵌在双环[ m .1.0]烷烃骨架中的环丙基甲硅烷基醚的生产。用氧化性电子转移试剂(例如Fe(III),Ce(IV)和Mn(III)盐)处理醚时,会生成扩环酮,并以中等至良好的产率转化为环状共轭烯酮。另外,还原氧化反应序列可以在一锅中成功进行。双环底物中环丙烷开环的区域选择性取决于所用的氧化剂。例如,FeCl 3促进的反应用吡啶导致预期的扩环过程,该过程涉及双环烷烃的内部键裂解并产生环烯酮作为最终产物。相反,与Ce(NH 4)2(NO 3)6或Mn(OAc)3作为氧化剂的反应通过外键裂解进行,得到α-碘甲基环烷酮。
Tris(trimethylsilyl)silane promoted radical reaction and electron-transfer reaction in benzotrifluoride
Tris(trimethylsilyl)silane (TTMSS) promoted free radical reaction in benzotrifluoride (BTF) was investigated. Compared to same reaction using environmentally less desirable tri-n-butyltin hydride (TBTH) in benzene, less quantity of BTF than that of benzene can be used because of slower hydrogen atom transfer from TTMSS than that from TBTH toward primary alkyl radicals. Also, electron-transfer reactions
A photo-reagent system of benzimidazoline and Ru(bpy)3Cl2 to promote hexenyl radical cyclization and Dowd–Beckwith ring-expansion of α-halomethyl-substituted benzocyclic 1-alkanones
undergo 5-exo hexenyl cyclization as well as sequential cyclization and ring-expansion (Dowd–Beckwith) reactions to form radicals that abstract hydrogen atoms from the radical cation of DMBIH to yield the observed products. The results of a study of the effects of substituents located on the 2-aryl ring of DMBIH suggest that steric and hydrogen-bonding interactions influence the nature of the reaction
Photoinduced electrontransfer (PET) reactionspromoted by 2-aryl substituted 1,3-dimethylbenzimidazolines (Ar-DMBIH) were investigated. Excited states of Ar-DMBIH, formed by irradiation using light above 360 nm, initiatePETreductions of various organic substrates, including transformations of epoxy ketones to aldols, free radical rearrangements such as the Dowd-Beckwith ring-expansion and 5-exo
Benzimidazoline-Dimethoxypyrene. An Effective Promoter System for Photoinduced Electron Transfer Promoted Reductive Transformations of Organic Compounds
2-(p-Methoxyphenyl)-1,3-dimethylbenzimidazoline (ADMBI) and 2-(o-hydroxyphenyl)-1,3-dimethylbenzimidazoline (HPDMBI) are used as reducing reagents in 1,8-dimethoxypyrene (1,8-DMP) sensitized, photoinduced electron transfer (PET) reactions. This system was effectively used for PET induced, reductive transformations of various organic substrates, including α,β-epoxy ketones, the olefin tethered 2-br