An Unprecedented Electronic Preference for the "Meta" Product in Diels-Alder Reactions of Ethynyldialkylboranes. -9-BBN as a Reactive and Versatile Dienophile

Article abstract of DOI:10.1021/jo00044a008

<(Trimethylsilyl)ethynyl>-9-BBN undergoes Diels-Alder reactions with acyclic dienes at 100 deg C to afford 1,4-cyclohexadienes in high yields.The novel regiochemistry of these reactions is consistent with an ab initio prediction of advanced bonding to boron in a <4 atom + 3 atom> transition state.