One-Pot Double-Annulation Strategy for the Synthesis of Unusual Fused Bis-Heterocycles
作者:Shukree Abdul-Rashed、Georgios Alachouzos、William W. Brennessel、Alison J. Frontier
DOI:10.1021/acs.orglett.0c01351
日期:2020.6.5
A novel metal-free double-annulation cascade for the construction of unusual fused heterocyclic systems is described. This simple protocol enables the sequential assembly of two rings in one pot from two simple precursors. Acidic conditions promote the condensation and the intramolecular alkynyl Prins reaction of an enyne or arenyne alcohol with a cyclic hemiaminal to form a five-, six-, or seven-membered
Total Synthesis of Polyene Natural Product Dihydroxerulin by Mild Organocatalyzed Dehydrogenation of Alcohols
作者:Hexin Xie、Shilei Zhang、Hao Li、Xinshuai Zhang、Sihan Zhao、Zian Xu、Xixi Song、Xinhong Yu、Wei Wang
DOI:10.1002/chem.201103325
日期:2012.2.20
Polyene synthesis: An efficient approach to the total synthesis of polyene naturalproduct dihydroxrulin (1) is described. A novel, mild, direct organocatalytic IBX‐mediated dehydrogenation process of simple alcohols to enals has been developed, which serves as a key step in the synthesis (see scheme).
Palladium‐Catalyzed Formal Hydroalkylation of Aryl‐Substituted Alkynes with Hydrazones
作者:Lin Yu、Leiyang Lv、Zihang Qiu、Zhangpei Chen、Ze Tan、Yu‐Feng Liang、Chao‐Jun Li
DOI:10.1002/anie.202005132
日期:2020.8.10
naturally abundant aldehydes, as both alkylation reagents and hydrogen donors. The hydroalkylation proceeds with high regio‐ and stereoselectivity to form (Z )‐alkenes, which are more difficult to generate compared to (E )‐alkenes. The reaction is compatible with a wide range of functional groups, including hydroxy, ester, ketone, nitrile, boronicester, amine, and halide groups. Furthermore, late‐stage modifications
Synthesis of bicyclic N,N-enaminals by cyclization of alk-4-ynals with aliphatic diamines in DMSO upon treatment with KOH
作者:V. D. Gvozdev、K. N. Shavrin、O. M. Nefedov
DOI:10.1007/s11172-013-0351-3
日期:2013.11
A cyclization of alk-4-ynals with aliphatic diamines in DMSO upon treatment with KOH was found to lead to bicyclic N,N-enaminals. The studies of this reaction showed that 1,3-diaminopropane and N-methyl-1,3-diaminopropane gave (E)-6-(arylmethylidene)octahydropyrrolo[1,2-a]pyrimidines in 45—78% yields, whereas 1,2-diaminoethane gave 5-(arylmethylidene)hexahydropyrrolo[1,2-a]imidazoles as mixtures of E- and Z-isomers in up to 75% total yield. The mechanism of these new cascade cyclization reactions includes formation of the equilibrium mixtures of imines and cyclic aminals with subsequent intramolecular hydroamination of the triple bond having considerable ionic character.