No abstract

1,1-Disubstituted vinyl triflates are synthesized by direct hydrotriflation of terminal alkynes employing a combination of TfOH and TMSN 3 in DCM at room temperature. Interestingly, under these conditions, only terminal alkynes were selectively converted to the corresponding vinyl triflates, while internal alkynes were not reacted. A broad range of substrates were successfully converted to the corresponding 1,1-disubstituted vinyl triflates in good to excellent yields even those with internal alkyne moieties present in the molecules.

We report a redox-neutral catalytic coupling of nitroalkanes and unactivated alkenes that proceeds by a directed carbopalladation mechanism. The reaction is uniquely enabled by the combination of PdI 2 as the precatalyst and HFIP solvent. Structurally complex nitroalkane products, including nitro-containing carbo-and heterocycles, are prepared under operationally convenient conditions without the need for toxic or corrosive reagents. Deuterium labeling experiments and isolation of a catalytically relevant intermediate shed light on the reaction mechanism. By taking advantage of different catalytic activation modes, we demonstrate orthogonal methods for site-selective functionalization of a polyfunctional nitroalkyl ketone. Density functional theory (DFT) calculations show that the carbopalladation transition state is stabilized by a Na•••I interaction and H•••I hydrogen bond with HFIP.

The generation of reactive carbocation intermediates from ortho-alkynylarylmethanol substrates was utilized as a means for the synthesis of aryl(1-indanyl)ketones . Substrates with a tertiary carbon at the β-position to the arene generated a carbocation intermediate via dehydration/protonation, followed by cyclization and hydration to give indanylketone products. For substrates with a quaternary carbon at that position, a carbocation intermediate was generated by protonation/elimination of water, followed by a 1,2-shift and a subsequent cyclization/hydration to give highly substituted indanylketones.