Three-step synthesis of an array of substituted benzofurans using polymer-supported reagents
作者:Jörg Habermann、Steven V. Ley、René Smits
DOI:10.1039/a904384e
日期:——
achieved by the bromination of acetophenones to α-bromoacetophenones by polymer-supported pyridiniumbromideperbromide (PSPBP). The subsequent clean substitution of the obtained bromides by phenols using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD-P) and cyclodehydration of the resulting α-phenoxyacetophenones using Amberlyst 15, affords pure products without the need for any chromatographic purification
selectively deprotonated generating an enolate intermediate, which upon treatment with paraformaldehyde undergoes an aldol–Tishchenko reaction, leading to relevant 1,2,3-triol fragments in a totally diastereoselective manner. The excellent stereocontrol in the generation of a quaternary stereocenter is attributed to stereoelectronic effects in the Evans intermediate. This methodology allows overcoming some