Synthesis and time resolved infrared analysis of photochemical oxiranyl carbene and diphenyl ketene precursors. Issue 43 (26th October 2016)

• Record Type: Journal Article
• Authors: Tippmann, Eric M.; Curtis, Ryan
• Is Part Of: Tetrahedron letters. Volume 57:Issue 43(2016)
• Page Start: 4785
• Page End: 4787
• Publication Date: 2016-10-26
• Subjects: Reactive intermediate -- Carbene -- Ketene -- Photochemistry; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tetlet.2016.08.039
• Languages: English
• ISSNs: 0040-4039

Abstract

Graphical abstract: Highlights: Common synthesis of carbene precursor resistant to oxiranyl carbene precursors. Rearrangement mechanism formed a photochemical source of diphenylketene. The production of diphenylketene was determined by time-resolved spectroscopy. Abstract: Synthesis of a nonnitrogenous phenanthrene-based precursor of oxiranyl carbene yielded a photochemical source for diphenyl ketene after an in situ intramolecular rearrangement. The initial carbene precursor targeted rearranged from a putative spiro-oxiranyl intermediate to a cyclobutanone. Photolysis of the phenanthrene–cyclobutanone generated an infrared signal centered at 2100 cm −1 consistent with diphenyl ketene formation. Time-resolved infrared spectroscopy followed the reaction progress and measured bimolecular rate constants ( k obs = 9.1 × 10 6 M −1 s −1 ; butyl amine) consistent with diphenyl ketene formation. Quenching experiments combined with Stern–Volmer kinetics suggests a radical pathway is likely involved in the formation of diphenyl ketene from the phenanthrene-based precursor. The generality of the rearrangement is also discussed.