Traceless Protection for More Broadly Applicable Olefin Metathesis.

Mu, Yucheng; Nguyen, Thach T.; van der Mei, Farid W.; Schrock, Richard R.; Hoveyda, Amir H.

An operationally simple in situ protection/deprotection strategy that significantly expands the scope of kinetically controlled catalytic Z‐ and E‐selective olefin metathesis is introduced. Prior to the addition of a sensitive Mo‐ or Ru‐based complex, treatment of a hydroxy‐ or a carboxylic‐acid‐containing olefin with commercially available HB(pin) or readily accessible HB(trip)2 (pin=pinacolato, trip=2,4,6‐tri(isopropyl)phenyl) for 15 min is sufficient for efficient generation of a desired product. Routine workup leads to quantitative deprotection. A range of stereochemically defined Z‐ and E‐alkenyl chlorides, bromides, fluorides, and boronates or Z‐trifluoromethyl‐substituted alkenes with a hydroxy or carboxylic acid group were thus prepared in 51–97 % yield with 93 to >98 % stereoselectivity. We also show that, regardless of whether a polar functional unit is present or not, a small amount of HB(pin) may be used to remove residual water, significantly enhancing efficiency.

ALKENES; METATHESIS reactions; BROMIDES; CARBOXYLIC acids; STEREOSELECTIVE reactions

Angewandte Chemie, 2019, Vol 131, Issue 16, p5419

0044-8249

Academic Journal

10.1002/ange.201901132