Preparation and reactivity of electron-poor 2-azadienes. Diels-Alder reaction with trans-cyclooctene.
摘要:
Di-, tri- and tetra- substituted 2-azadienes 3 underbar with electron withdrawing groups have been obtained by Aza-Wittig reaction of N-vinylic phosphazenes with carbonyl compounds. The Diels-Alder reaction of 3 underbar with trans-cyclooctene has also been explored.
Aza-Wittig reaction of N-vinylic phosphazenes with carbonyl compounds. Azadiene-mediated synthesis of dihydropyridines and pyridines
作者:Francisco Palacios、Gloria Rubiales
DOI:10.1016/0040-4039(96)01352-4
日期:1996.8
diphenylmethylphosphine 4 with carbonylcompounds leads to the formation of 2-azadienes derived from β-aminoacids 5. Dimerization of 2-azadienes 5c,d and reaction of compounds 5 with phosphazene 4 or enemine 6 affords substituted dihydropyridines 7 and 8. Aza-Wittig reaction of phosphazenes 4 with α,β-unsaturated aldehydes gives 3-azatrienes 12, which are easily converted into pyridines 13.
Synthesis and Reactivity of Electron-Poor 2-Azadienes. [4 + 2] Cycloaddition Reactions with Alkenes and Enamines
作者:Francisco Palacios、Itziar Perez de Heredia、Gloria Rubiales
DOI:10.1021/jo00113a017
日期:1995.4
Electron deficient 2-azadienes derived from beta-amino acids 3 are obtained by aza-Wittig reaction of N-vinylic phosphazenes 4 with carbonyl compounds. Inverse electron demand Diels-Alder reaction of azadienes 3 with trans-cyclooctene 7 and cis,trans-cyclooctadiene 8 leads to the formation of trans-cycloalkanotetrahydropyridines 10. Heterodienes 3 also react with enamines 13, 14, and 18 affording pyridine derivatives 16, 17, and 20 in a regioselective fashion. Norbornadiene 11, a less strained olefin than cycloalkenes 7 and 8, requires the presence of lithium perchlorate as catalyst in a nonaqueous solvent like ether, to give cycloadducts 12.