A regioselective synthesis of the dihydroquinolin-4-one <b>4</b> is achieved from the aryne-mediated annulation of an <i>o</i>-(trimethylsilyl)aryl triflate <b>1</b> with <i>N</i>-tosyl-2-enamide <b>2</b> in the presence of TBAT in toluene, whereas the chroman-4-imine <b>5</b> is formed from the reaction of <b>1</b> with <i>N</i>-(<i>tert</i>-butylsulfinyl)-2-enamide <b>3</b> and TBAF in THF. Governing factors for regioselectivity have been accounted for as strong steric and electronic effects between <i>N</i>-toluenesulfonyl and <i>N</i>-<i>tert</i>-butylsulfinyl groups in <b>2</b> and <b>3</b>. The methods described herein are successful with various substrates <b>1</b> with <b>2</b> or <b>3</b> in high levels of regioselectivity, and diastereoselectivity for <b>5</b>.

Concise syntheses of naturally occurring γ-butenolides (+)-xylogiblactones B and C have been achieved for the first time starting from commercial methyl crotonate in 5-8 steps. The synthetic course involves allenoate γ-addition to racemic aldehydes through a kinetic resolution to establish the required stereochemical framework as center and axial chirality and subsequent oxacyclization via gold catalysis to complete the (+)-xylogiblactone skeleton. Both key transformations proceed in a regio- and stereospecific manner. This outcome relies on finding an efficient synthetic method for racemic aldehydes as precursors for the kinetic resolution. Completion of the synthesis provides stereochemical clarification for (+)-xylogiblactones B and C.