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Thesynthesis of the C1–C18 fragment of the myxobacteriametabolite rhizopodin is described. Initial attempts at installingthe E,E-diene via cross couplingwith an oxazole fragment gave poor results. An alternative approach,in which the diene was formed prior and the oxazole introduced byan acylation/O,N-shift protocol, gave the C1–C18fragment 2of rhizopodin (1). [ABSTRACT FROM AUTHOR]

The early stages of the retro-Diels-Alder reaction are clearly apparent in the structures of the cycloadducts formed between furan or 5-trimethylsilylcyclopentadiene with maleic anhydride and N-methylmaleimide. The degree of lengthening of the C-C bonds that break in this reaction is clearly related to the known reactivity of these cycloadducts toward this reaction. In the structures of the cycloadducts 21 and 22 derived from 2-methoxyfuran, the early stages of an alternative fragmentation reaction are apparent, consistent with the reactivity of these compounds in solution. [ABSTRACT FROM AUTHOR]

Gas-phase carbon-carbon bond forming reactions, catalyzed by group 10 metal acetate cations [(phen)M(O2CCH3)]+ (where M = Ni, Pd or Pt) formed via electrospray ionization of metal acetate complexes [(phen)M(O2CCH3)2], were examined using an ion trap mass spectrometer and density functional theory (DFT) calculations. In step 1 of the catalytic cycle, collision induced dissociation (CID) of [(phen)M(O2CCH3)]+ yields the organometallic complex, [(phen)M(CH3)]+, via decarboxylation. [(phen)M(CH3)]+ reacts with allyl acetate via three competing reactions, with reactivity orders (% reaction efficiencies) established via kinetic modeling. In step 2a, allylic alkylation occurs to give 1-butene and reform metal acetate, [(phen)M(O2CCH3)]+, with Ni (36%) > Pd (28%) > Pt (2%). Adduct formation, [(phen)M(C6H11O2)]+, occurs with Pt (24%) > Pd (21%) > Ni(11%). The major losses upon CID on the adduct, [(phen)M(C6H11O2)]+, are 1-butene for M = Ni and Pd and methane for Pt. Loss of methane only occurs for Pt (10%) to give [(phen)Pt(C5H7O2)]+. The sequences of steps 1 and 2a close a catalytic cycle for decarboxylative carbon-carbon bond coupling. DFT calculations suggest that carbon-carbon bond formation occurs via alkene insertion as the initial step for all three metals, without involving higher oxidation states for the metal centers. [ABSTRACT FROM AUTHOR]

A novel free radical trapping reaction based on a stepwise radical reversible addition-fragmentation mechanism has been utilized to synthesize a series of acenaphthenyl dimers and trimers. The synthetic procedure involves the reaction of acenaphthylene with dithiobenzoate compounds (S= C(Ph)-SR) in the presence of a free radical initiator followed by reduction of the dithiobenzoyl end group with tributyltin hydride. Stereoisomers of the compounds have been isolated and their structures determined by proton NMR and X-ray crystallography. The solution fluorescence of the compounds has been characterized to reveal the requirements for intramolecular excimer (excited-state dimer) formation. Only in compounds containing identical stereochemical arrangements of adjacent acenaphthenyl groups is excimer fluorescence observed following photoexcitation. [ABSTRACT FROM AUTHOR]