title: Synthesis, structure and emission properties of spirocyclic benzofuranones and dihydroindolones: a domino insertion-coupling-isomerization- Diels-Alder approach to rigid fluorophores.
abstract: An alkynoyl ortho-iodo phenolester or alkynoyl ortho-iodo anilides and propargyl allyl ethers react under Sonogashira coupling conditions in the sense of an insertion-coupling-isomerization-Diels-Alder hetero domino reaction to furnish (tetrahydroisobenzofuran)-spirobenzofuranones and -spirodihydroindolones in good yields. Many representatives can be crystallized and single crystal structure analyses display steric and electronic substituent effects on the torsional angles of the terminal (hetero)aryl groups and the central cis,trans-butadiene fragment. DFT computations reveal that in the final pericyclic step the Diels-Alder termination is by far thermodynamically and kinetically favored over a possible Claisen rearrangement. Compounds of this new class of spirocyclic compounds possess large Stokes shifts and fluoresce intensively with blue over green to orange colors. As a consequence of the spirocyclic rigidity fluorescence lifetimes and quantum yields are rather high in some cases.
authors.affiliation: Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: D'Souza
authors.forename: Alexander
authors.initials: A
authors.lastname: Kiel
authors.forename: Dirk-Peter
authors.initials: DP
authors.lastname: Herten
authors.forename: Frank
authors.initials: F
authors.lastname: Rominger
authors.forename: Thomas J J
authors.initials: TJ
authors.lastname: Müller
mesh_terms: D001572:Benzofurans / Q000138:chemical synthesis / Q000737:chemistry; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D003500:Cyclization; D005453:Fluorescence; D007211:Indoles / Q000138:chemical synthesis / Q000737:chemistry; D047028:Macrocyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013141:Spiro Compounds / Q000138:chemical synthesis / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D001572:Benzofurans; D007211:Indoles; D047028:Macrocyclic Compounds; D013141:Spiro Compounds