Synthesis of Linear (Z)‐α,β‐Unsaturated Esters by Catalytic Cross‐Metathesis. The Influence of Acetonitrile

Abstract

Kinetically-controlled catalytic cross-metathesis reactions that generate (Z)-α,β-unsaturated esters selectively are disclosed. A key finding is that the presence of acetonitrile obviates the need for using excess amounts of a more valuable terminal alkene substrates. On the basis of X-ray structure and spectroscopic investigations a rationale for the positive impact of acetonitrile is provided. Transformations leading to various E,Z-dienoates are highly Z-selective as well. Utility is highlighted by application to stereoselective synthesis of the C1–C12 fragment of biologically active natural product (−)-laulimalide.

Decarboxylative alkenylation

“…Both cis and trans alkenylzinc reagents can be prepared with high geometric purity, leading smoothly to 27 and 28 . This method provides a complimentary strategy to olefin cross-metathesis 18 to access such structures. It is also worth noting that the butenolide ( 29 ) has never been prepared before.…”

Stereoselective Construction of (E,Z)‐1,3‐Dienes and Its Application in Natural Product Synthesis

“…More recently, the rise of Z ‐selective ring‐ and cross‐metathesis catalysts has enabled new developments in E,Z ‐diene construction [183–186] . Molybdenum‐catalysed, Z ‐selective cross‐metathesis reactions have been developed by Hoveyda and Schrock, and their potential is highlighted by their application to construct Z ‐ and Z,E ‐dienylboron(pin) double‐bond subunits (Scheme 80).…”

“…However, a rather encumbered carbene catalyst was necessary to More recently, the rise of Z-selective ring-and cross-metathesis catalysts has enabled new developments in E,Z-diene construction. [183][184][185][186] Molybdenumcatalysed, Z-selective cross-metathesis reactions have been developed by Hoveyda and Schrock, and their potential is highlighted by their application to construct Z-and Z,E-dienylboron(pin) double-bond subunits (Scheme 80). Dienylboron(pin) (205) was next used in the construction of the 30-membered macrolide disorazole C 1 through inter-and intramolecular double, Pdcatalysed, cross-coupling reactions (see section 2.2).…”

Calyciphylline B-type Alkaloids: Evolution of a Synthetic Strategy to (−)-Daphlongamine H

“…9,138.0,134.5,128.3,127.8,127.1,117.3,116.5,80.4,58.5,57.8,55.2,38.4,28.2,neat) . Synthesis of tert-Butyl (S)-3-((2-bromoallyl) ((S)-1-phenylethyl)amino)-2-methylenepent-4-enoate (66). n-Butyllithium solution (2.5 M in hexanes, 6.84 mL, 17.1 mmol, 2.5 equiv) was added dropwise to a solution of DIPA (2.49 mL, 17.8 mmol, 2.6 equiv) in THF (20 mL) at −78°C.…”