A Brønsted acid mediated cascade enone synthesis from aldehydes containing a tethered propargylsilane.
MeSO3H effects the intramolecular allenylation of a series of aldehydes 1 to provide allenyl alcohol product 3 as a single diastereoisomer. Cyclization proceeds rapidly at -78 degrees C. However, when the reaction is performed at room temperature, aldehyde 1 provides enone product 7 instead. A mechanism for the formation of this product is proposed in which the initially formed allenyl alcohol 3 undergoes dehydration to provide an allyl carbocation, which is trapped with water, thereby installing the enone.
Ramalho
Rui
R
School of Chemistry, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Jervis
Peter J
PJ
Kariuki
Benson M
BM
Humphries
Alexander C
AC
Cox
Liam R
LR
D000143:Acids / Q000737:chemistry*; D000447:Aldehydes / Q000737:chemistry*
D000143:Acids; D000447:Aldehydes