presence of the N-heterocyclic carbene gold catalyst (NHC-AuIPr, 7), propargyl esters 1a–f and 13 undergo a [4C+3C] cycloaddition reaction with cyclopentadiene and furan under mild conditions. The evidence suggests that the formation of the seven-membered ring occurs by a direct cycloaddition process, rather than a stepwise cyclopropanation/Cope rearrangement sequence.
Divergent Elementoboration: 1,3‐Haloboration versus 1,1‐Carboboration of Propargyl Esters
作者:Lewis C. Wilkins、Yashar Soltani、James R. Lawson、Ben Slater、Rebecca L. Melen
DOI:10.1002/chem.201801493
日期:2018.5.23
This work showcases the 1,3‐haloboration reaction of alkynes in which boron and chlorine add to propargyl systems in a proposed sequential oxazoliumborate formation with subsequent ring‐opening and chloride migration. In addition, the functionalization of these propargyl esters with dimethyl groups in the propargylic position leads to stark differences in reactivity whereby a formal 1,1‐carboboration
Activation of Alkynes with B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> – Boron Allylation Reagents Derived from Propargyl Esters
作者:Max M. Hansmann、Rebecca L. Melen、Frank Rominger、A. Stephen K. Hashmi、Douglas W. Stephan
DOI:10.1021/ja4110842
日期:2014.1.15
Novel allyl boron compounds are readily synthesized via rearrangementreactions between Lewis acidic B(C6F5)3 and propargyl esters. These reactions proceed through an initial cyclization followed by ring-opening and concurrent C6F5-group migration. In the absence of disubstitution adjacent to the ester oxygen atom, an allyl boron migration rearrangement leads to formal 1,3-carboboration products. These