通过选择性能量转移催化产生了一种新型的sp 3类N 中心自由基。在光激发下,在 Ir 配合物存在下N-吲哚碳酸酯的均裂 N-O 键断裂产生以 N 和 O 为中心的自由基。吲哚 C3 位的高自旋密度导致自由基与以 O 为中心的自由基复合,从而提供有价值的 3-氧吲哚衍生物而无需脱羧。还证明了所需产物向各种分子的转化。
通过选择性能量转移催化产生了一种新型的sp 3类N 中心自由基。在光激发下,在 Ir 配合物存在下N-吲哚碳酸酯的均裂 N-O 键断裂产生以 N 和 O 为中心的自由基。吲哚 C3 位的高自旋密度导致自由基与以 O 为中心的自由基复合,从而提供有价值的 3-氧吲哚衍生物而无需脱羧。还证明了所需产物向各种分子的转化。
5-Nitroisocoumarins from tandem Castro–Stephens coupling—6-endo-dig cyclisation of 2-iodo-3-nitrobenzoic acid and arylethynes and ring-closure of methyl 2-alkynyl-3-nitrobenzoates with electrophiles
作者:Esther C.Y. Woon、Archana Dhami、Mary F. Mahon、Michael D. Threadgill
DOI:10.1016/j.tet.2006.03.005
日期:2006.5
Reaction of 2-iodo-3-nitrobenzoic acid with arylalkynyl copper(I) reagent gave 3-aryl-5-nitroisocoumarins. Castro-Stephens coupling was followed by in situ Cu-catalysed ring-closure. H-1 NMR and X-ray crystallography showed the cyclisations to be 6-endo, contrasting with reports of 5-exo cyclisation of analogous 2-iodobenzoate esters with alkynes. Sonogashira couplings of methyl 2-iodo-3-nitro-benzoate with phenylacetylene and with trimethylsilylacetylene gave the corresponding 2-alkynyl-3-nitrobenzoate esters. With HgSO4, the phenylalkyne underwent 6-endo cyclisation to give 5-nitro-3-phenylisocoumarin. The disubstituted alkyne esters gave 4-phenylselenylisocoumarins with PhSeCl. 5-Nitro-3-phenyl-4-phenylselenylisocoumarin shows significant sterically-driven distortion of the isocoumarin ring. Reaction of methyl 3-nitro-2-phenylethynylbenzoate with ICI gave the 4-iodoisocoumarin. Thus the nitro group tends to direct these electrophile-driven cyclisations towards the 6-endo mode. (c) 2006 Elsevier Ltd. All rights reserved.