Synthesis of Substituted 1<i>H</i>-Indazoles from Arynes and Hydrazones
作者:Pan Li、Chunrui Wu、Jingjing Zhao、Donald C. Rogness、Feng Shi
DOI:10.1021/jo202598e
日期:2012.4.6
The 1H-indazole skeleton can be constructed by a [3 + 2] annulation approach from arynes and hydrazones. Under different reaction conditions, both N-tosylhydrazones and N-aryl/alkylhydrazones can be used to afford a variety of indazoles. The former reaction affords 3-substituted indazoles either via in situ generated diazo compounds or through an annulation/elimination process. The latter reaction leads to 1,3-disubstituted indazoles likely through an annulation/oxidation process. The reactions operate under mild conditions and can accommodate aryl, vinyl, and less satisfactorily, alkyl groups.
Rapid Access to α-Alkoxy and α-Amino Acid Derivatives through Safe Continuous-Flow Generation of Diazoesters
作者:Hannah E. Bartrum、David C. Blakemore、Christopher J. Moody、Christopher J. Hayes
DOI:10.1002/chem.201101590
日期:2011.8.22
highly efficient continuous‐flow process has been developed for the synthesis of diazoesters from arylsulfonylhydrazones by means of in‐flow Bamford–Stevens reactions. Furthermore, a range of α‐alkoxy and α‐amino acid derivatives have been prepared in excellent yields through rhodium(II)‐mediated OH and NHinsertions, without the need to isolate or handle the potentially hazardous diazo species (see
instability and unavailability of donor/donor diazo compounds. Considering all these existing challenges, herein, a metal-free strategy is reported to achieve N–H insertions via coupling donor/donor diazo precursors (N-tosylhydrazones) with a plethora of amines including aminopyridines, anilines, aliphatic amines, and other nucleophiles such as imidazoles, pyrroles, and indoles. Expediently, β-amino esters