Guiding a divergent reaction by photochemical control: bichromatic selective access to levulinates and butenolides. Issue 5 (5th January 2018)

• Record Type: Journal Article
• Authors: Sutar, Revannath L.; Sen, Saumik; Eivgi, Or; Segalovich, Gal; Schapiro, Igor; Reany, Ofer; Lemcoff, N. Gabriel
• Is Part Of: Chemical science. Volume 9:Issue 5(2018)
• Page Start: 1368
• Page End: 1374
• Publication Date: 2018-01-05
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c7sc05094a
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : Allylic and acrylic substrates may be efficiently transformed by a sequential bichromatic photochemical process into derivatives of levulinates or butenolides with high selectivity when phenanthrene is used as a regulator. Abstract : Allylic and acrylic substrates may be efficiently transformed by a sequential bichromatic photochemical process into derivatives of levulinates or butenolides with high selectivity when phenanthrene is used as a regulator. Thus, UV-A photoinduced cross-metathesis (CM) couples the acrylic and allylic counterparts and subsequent UV-C irradiation initiates E – Z isomerization of the carbon–carbon double bond, followed by one of two competing processes; namely, cyclization by transesterification or a 1, 5-H shift and tautomerization. Quantum chemical calculations demonstrate that intermediates are strongly blue-shifted for the cyclization while red-shifted for the 1, 5-H shift reaction. Hence, delaying the double bond migration by employing UV-C absorbing phenanthrene, results in a selective novel divergent all-photochemical pathway for the synthesis of fundamental structural motifs of ubiquitous natural products.