20843-07-6Relevant articles and documents
Cycloaddition of C-3 substituted furans. Stereoselectivity induced by coordination effects
Montana, Angel M.,Castellvi, Maria,Batalla, Consuelo,Grima, Pedro M.,Font-Bardia, Merce
, p. 9982 - 9998,17 (2012)
Several C-3 substituted furans with chelating groups have been reacted with 2,3-dibromo-3-pentanone in the presence of a reducing metal, resulting in the formation of [4+3]-cycloadducts with complete cis-trans and endo-exo diastereoselectivity and in excellent yield. A certain variability of the conversion and reaction yield could be observed, when changing the reaction conditions, but in all cases the stereoselectivity was complete, compared to that of C-3 substituted furans with non-chelating groups. Also, a general method of assignment of stereochemistry of cycloadducts has been established by NMR, considering diagnostic patterns of signals with different multiplicity and chemical shifts depending on the stereochemistry of diastereomeric cycloadducts.
Cycloaddition of C-3 substituted furans. Stereoselectivity induced by coordination effects
Monta?a, ángel M.,Grima, Pedro M.,Castellví, María,Batalla, Consuelo,Font-Bardia, Mercè
, p. 9982 - 9998 (2013/01/14)
Several C-3 substituted furans with chelating groups have been reacted with 2,3-dibromo-3-pentanone in the presence of a reducing metal, resulting in the formation of [4+3]-cycloadducts with complete cis-trans and endo-exo diastereoselectivity and in excellent yield. A certain variability of the conversion and reaction yield could be observed, when changing the reaction conditions, but in all cases the stereoselectivity was complete, compared to that of C-3 substituted furans with non-chelating groups. Also, a general method of assignment of stereochemistry of cycloadducts has been established by NMR, considering diagnostic patterns of signals with different multiplicity and chemical shifts depending on the stereochemistry of diastereomeric cycloadducts.
Synthesis of a dimethylfuran-containing macrolide insect pheromone
Petroski, Richard J.,Bartelt, Robert J.,Vermillion, Karl
experimental part, p. 1389 - 1405 (2009/09/26)
The synthetic pathway to the furan-containing macrolide pheromone (1) of Galerucella beetles was shortened from 13 steps in the original synthesis to 10 steps, and the overall yield was increased greater than six-fold. A concise Reformatsky-based sequence of reactions was utilized to construct the key precursor, 2,3-dimethyl-2-butenolide. Reduction of the butenolide with diisobutylaluminum hydride afforded 3,4-dimethylfuran. A one-pot sequence of lithiation, alkylation by a tetrahydropyranyl (THP)-containing iodide, a second lithiation, and, finally, formylation gave the required tetrasubstituted furan intermediate, 3,4-dimethyl-5-[5-(tetrahydrofuran-2-yloxy)pentyl]-2-furaldehyde. To continue construction of the three-carbon acyl side chain, the aldehyde was converted to an unsaturated ester by a Horner-Wadsworth-Emmons (HWE) condensation with triethyl phosphonoacetate. After reduction of the double bond in the ester side chain and removal of protective groups, the lactone ring was closed using the Mitsunobu method, which is milder, is simpler, and could be accomplished with less solvent than the previous (Yamaguchi) method.
Gas-phase heteroaromatic substitution. 14. Attack of dimethylfluoronium ion on 2- and 3-methyl-pyrroles, -furans, -and thiophenes
Cecchi, Patrizio,Pizzabiocca, Adriano,Renzi, Gabriele,Sparapani, Cinzia,Speranza, Maurizio
, p. 2094 - 2103 (2007/10/02)
The gas-phase methylation of 2- and 3-methyl-pyrroles (2P and 3P), -furans (2F and 3F), and thiophenes (2T and 3T) by (CH3)2F+ ions, from γ-radiolysis of CH3F, has been investigated at pressures ranging from 50 to 760 Torr, in the presence of a thermal radical scavenger (O2) and variable concentrations of an added base (NMe3: 0-10 Torr).The mechanism of the methylation process is discussed and the intrinsic positional selectivity of the (CH3)2F+ ions evaluated in the framework of the Charge and Frontier Orbital Control concept.Owing to the very large energy gap between the LUMO of (CH3)2F+ and the HOMOs of the selected heteroaromatic substrates, their gas-phase methylation is characterized by a distinct affinity of the ionic electrophile toward those substrates positions with the highest net negative charge, i.e., the C3 in 2P (100percent), the C4 in 3P (100percent), the heteroatom of 2F and 3F (>80percent), the C5 of 2T (32percent), and the C2 of 3T (47percent).Analysis of the methylated product distribution from 2F and 3F as a function of the experimental conditions reveals that the interaction of the (CH3)2F+ with the heteroatom of furans gives rise to the reversible formation of two sets of electrostatic adducts, i.e., a "chelate" adduct (III) and a single proton-bonded adduct (IV), the first rapidly evolving to the α-substituted heteroarenium intermediate by proximity effects and the latter slowly rearranging to the chelate structure III.Formation of these categories of electrostatic adducts from furans, which is much less extensive in the case of thiophenes and absent in pyrroles, accounts for the apparent pronounced affinity of gaseous alkylating electrophiles, irrespective of their LUMO energy, for the α carbons of furans. Key words: gas-phase ion chemistry, electrophilic aromatic substitution, radiolysis, dimethylfluoronium ions, methylated heteroarenes.
Etude des transformations catalytiques sur alumine de β-tetrahydrofurylmethanols
Infarnet, Yves,Accary, Armand,Huet, Jean
, p. 261 - 266 (2007/10/02)
The products obtained by treatment of β-tetrahydrofurylmethanols at 310-330 deg C, using alumina as catalyst are studied.The nature of the products-furans, tetrahydrofurans, aliphatic and cyclic dienes-shows that beside the simple dehydration side reactions take place leading, as the case may be, to dehydrogenation, raduction, ring opening and fragmentation.
