Diastereoselective and Enantioselective Heck Alkenylation of Cyclopent‐3‐en‐1‐ylmethanol with Alkenyl Triflates and Evaluation of Noncovalent Effects

This work describes an effective method to obtain chiral vinyl cyclopentenols with a high degree of enantioselectivity and diastereoselectivity through Heck desymmetrization of cyclopent-3-en-1-ylmethanol using vinyl triflates as coupling agents and chiral N,N ligands. This Heck vinylation protocol allowed the synthesis of several structurally complex cyclopentenols in isolated yields of up to 80 % in enantiomeric ratios of up to 97 : 3 and diastereoselectivities higher than 20 : 1 in most cases. Experiments using (E) or (Z) vinyl triflates, and desymmetrization of protected olefin 1-(cyclopent-3-en-1-ylmethoxy)-4-nitrobenzene (17) were instrumental in rationalizing the observed diastereoselectivities of Heck products involving the interaction of vinyl triflate carbonyl and the hydroxyl group moiety of the substrate with the cationic Pd(II) complex. The absolute configuration of the vinylated Heck products was determined by Vibrational Circular Dichroism (VCD) spectroscopy.