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All total 5 Articles be foundVisible-Light-Promoted, Catalyst-Free Gomberg-Bachmann Reaction: Synthesis of Biaryls
Lee, Juyoung,Hong, Boseok,Lee, Anna
, p. 9297 - 9306 (2019/08/12)
Biaryls were synthesized via a novel visible-light-promoted Gomberg-Bachmann reaction that does not require a photosensitizer or any metal reagents. The formation of an electron donor-acceptor complex between aryl diazonium salts and pyridine allows, under visible-light irradiation, the synthesis of biaryls in moderate-to-high yields.
Mild and selective deprotection method of acetylated steroids and diterpenes by dibutyltin oxide
Wang, Shao-Min,Zhang, Yan-Bing,Liu, Hong-Min,Yu, Guo-Bin,Wang, Ke-Rang
, p. 26 - 30 (2007/10/03)
Dibutyltin oxide (DBTO) was first utilized for the deacetylation of steroid and diterpene esters. The results showed the deprotection of acetylated steroids and diterpenes separately with moderate catalysis dibutyltin oxide in methanol selectively removed part acetyl groups of these substrates, whereas several functional groups of the steroids and diterpenes were retained and neither isomerization nor degradation of these substrates was observed. It seems that the acetyl groups with lower steric hindrance or near carbonyl, alkoxy, or hydroxyl groups can be cleaved by the reaction, whereas the acetyl groups with higher steric hindrance or without carbonyl, alkoxy, or hydroxyl groups neighboring were retained under the same conditions. One of the interesting results obtained was the selective hydrolysis of the 3β-O-acetyl group in the presence of the 6β group in 3β,6β-Di-O-acetyl-5α-hydroxypregn-16-en-20-one. This allows for subsequent introduction of one unit at C-3 and the other unit at C-6. This procedure is useful for the synthesis of a series of closely related isomers of 3β,5α,6β-trihydroxypregn-16-en-20-one and other widespread polyhydroxysteroids in marine organisms and some terrestrial species.
Aryl radicals from hexazadienes and tetrazenes
Mackay, Donald,McIntyre, Deane Douglas
, p. 990 - 999 (2007/10/02)
Aryl radicals are produced from both ends of the hexazadienes 1 and 2 and from the tetrazene 3, either thermally or photolytically.They attack aromatic compounds in the nucleus, the yield of biaryl being in the range 40-70percent, though it can be made nearly quantitative by using m-dinitrobenzene as additive.The aryl radicals also oxidize 2-propanol to acetone, the reaction products being the halogenobenzene and 1,2-diacetylhydrazine.Photolysis of 1 goes mainly by way of the tetrazene 3, and this may also be a significant pathway in the thermal reaction.Azodiacetylis an intermediate in the thermal reaction of 1 with 2-propanol and may be generally so in all its reactions.Radical induced decomposition is believed to be important in the reactions of 1, 2, and 3, and it is probably responsible for the formation of 1-acetyl-1-arylhydrazines, routinely produced in yields up to 25percent.
