Stereoselective E/Z-photoisomerization of cyclooctene using 2, 4-pentanediol chiral tether. Issue 2 (15th February 2017)

• Record Type: Journal Article
• Authors: Song, Kuifeng; Fujita, Morifumi; Okuyama, Tadashi; Sugimura, Takashi
• Is Part Of: Tetrahedron, asymmetry. Volume 28:Issue 2(2017)
• Page Start: 296
• Page End: 301
• Publication Date: 2017-02-15
• Subjects: Asymmetry (Chemistry) -- Periodicals; 547.005
• DOI: 10.1016/j.tetasy.2017.01.007
• Languages: English
• ISSNs: 0957-4166

Abstract

Graphical abstract: Abstract: The photoisomerization, epoxidation, and cyclopropanation of chiral 2, 4-pentanediol tethered cyclooctene were explored to examine the stereocontrollability of the tether. Photoisomerization of (2 R, 4 R )-2, 4-pentanediol-tethered cyclooctene achieved a de of 20% at a high Z / E ratio of 0.80 at 25 °C, while (2 S, 4 R )-2, 4-pentanediol-tethered cyclooctene yielded a lower de in spite of an even higher Z / E ratio. The epoxidation and cyclopropanation of 2, 4-pentanediol tethered cyclooctene resulted in lower stereoselectivity compared with those of vinyl ether. We propose that the low de of the reactions of 2, 4-pentanediol tethered cyclooctene is not attributable to the low stereocontrollability of 2, 4-pentanediol tether, but due to the conformational multiplicity of the reactant site. Abstract : (2 R, 4 R )-4-(( E )-Cyclooctenylmethoxy)pentan-2-ol: C14 H26 O2 [ α ] D 20 = −79.3 ( c 0.96, chloroform) Preparation via the reaction of 1-(bromomethyl)cyclooct-1-ene with monosodium salt of (2 R, 4 R )-2, 4-pentanediol Absolute configuration: (2 R, 4 R ) Abstract : (2 R, 4 R )-4-(( E )-Cyclooctenylmethoxy)pentan-2-yl benzoate: C21 H30 O3 [ α ] D 20 = −83.3 ( c 1.02, chloroform) Preparation via the reaction of (2 R, 4 R )-4-(( E )-cyclooctenylmethoxy)pentan-2-ol with benzoyl chloride Absolute configuration: (2 R, 4 R ) Abstract : (2 S, 4 R )-4-(( E )-Cyclooctenylmethoxy)pentan-2-ol: C14 H26 O2 [ α ] D 20 = −17.1 ( c 0.98, chloroform) Preparation via the reaction of (2 R, 4 R )-4-(( E )-cyclooctenylmethoxy)pentan-2-yl benzoate with NaOH (aq, 20%) in methanol at 50 °C Absolute configuration: (2 S, 4 R ) Abstract : (2 S, 4 R )-4-(( E )-Cyclooctenylmethoxy)pentan-2-yl benzoate: C21 H30 O3 [ α ] D 20 = +18.5 ( c 1.05, chloroform) Preparation via Mitsunobu reaction of (2 R, 4 R )-4-(( E )-cyclooctenylmethoxy)pentan-2-ol with benzoic acid Absolute configuration: (2 S, 4 R )