An efficient and practical entry to 2-amido-dienes and 3-amido-trienes from allenamides through stereoselective 1,3-hydrogen shifts

• Ryuji Hayashi,
• John B. Feltenberger,
• Andrew G. Lohse,
• Mary C. Walton and
• Richard P. Hsung

Beilstein J. Org. Chem. 2011, 7, 410–420, doi:10.3762/bjoc.7.53

• ][97][98][99]) to access cyclic 2-amido-dienes that are quite rare (for examples see [100][101][102]). Chiral amido-triene 22 underwent electrocyclization efficiently to give chiral cyclic 2-amido-diene 44a in 84% yield. Although obtained in only 35% yield, the achiral cyclic 2-amido-diene 45 could

• (135 °C), thereby implying an accelerated process of electrocyclization. This feature is consistently observed in related ring-closures of 1,3,5-hexatrienes with an electron-donating substituent at the C3 position of the triene [94][95][96][97][98][99] (for theoretical studies on substituent effects on

Expedient syntheses of the N-heterocyclic carbene precursor imidazolium salts IPr·HCl, IMes·HCl and IXy·HCl

• Lukas Hintermann

Beilstein J. Org. Chem. 2007, 3, No. 22, doi:10.1186/1860-5397-3-22

• involving a 1,5-dipolar electrocyclization is proposed. Background Imidazolylidene carbenes have been investigated as ligands in coordination chemistry, as powerful steering/controlling elements in transition-metal catalysis,[1][2] and more recently as metal-free catalysts for organic reactions[3][4]. Some

• can be induced by chloromethylethers. Loss of HCl from B (presumably to A, which is a monobasic species)[13] gives an imino-azomethin-ylide 1,5-dipole C (only one mesomeric structure shown), which will undergo 1,5-dipolar cyclization (6π electrocyclization) [18][19][20] to an oxy-imidazoline D

• full experimental data. The carbenes IPr, IMes, IXy and their imidazolium salt precursors Synthetic routes to and diazadiene precursors for imidazolium salts. The imidazolium salt synthesis as a 1, 5-dipolar electrocyclization. Potential side-reactions in the imidazolium salt synthesis. Optimization of

Trapping evidence for the thermal cyclization of di-(o-acetylphenyl)acetylene to 3,3'-dimethyl- 1,1'-biisobenzofuran

• Charles P. Casey,
• Neil A. Strotman and
• Ilia A. Guzei

Beilstein J. Org. Chem. 2005, 1, No. 18, doi:10.1186/1860-5397-1-18

• phenylcarbenes to isobenzofurans. Ring opening of 2-furylcarbenes to alk-2-en-4-yn-1-ones. Coupled coarctate cyclization and 6π electrocyclization. Supporting Information Supporting Information File 26: bisfuran-supportinginfo.doc 100 Kb Acknowledgements Financial support from the National Science Foundation