RegioselectiveAryne Annulations of <i>N</i>‑Tosyl-2-enamides and <i>N</i>-<i>tert</i>-Butylsulfinyl-2-enamides for theConstruction of Dihydroquinolin-4-oneand Chroman-4-imine Units

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>.