Norbornadiene

About: Norbornadiene is a research topic. Over the lifetime, 2389 publications have been published within this topic receiving 38603 citations.

Camphor-Derived, Chelating Auxiliaries for the Highly Diastereoselective Intermolecular Pauson−Khand Reaction: Experimental and Computational Studies

Abstract: A family of enantiomerically pure (2R)-10-(alkylthio)isoborneols [methylthio (1), neopentylthio (2), phenylthio (3)], specifically designed as chiral auxiliaries suitable for chirality transfer to cobalt in Pauson−Khand reactions, has been synthesized. The dicobalt hexacarbonyl complexes of the alkoxyacetylenes derived from these alcohols (10a−12a) can be converted to the rather stable, internally chelated, pentacarbonyl complexes 10b−12b by treatment with NMO. The intermolecular Pauson−Khand reactions of 10b−12b with strained olefins take place with synthetically useful rates at low temperatures (down to −20 °C), with high yields and diastereoselectivities: norbornene (77%; 92:8), norbornadiene (82%; 96:4), bicyclo[3.2.0]hept-6-ene (91%; 93:7). The major diastereomer of the adduct of 10b with norbornadiene, 14, has been used as the starting point for a synthesis of (S)-(−)-4-alkyl-2-cyclopentenones through a sequence consisting of completely diastereoselective conjugate addition, reductive cleavage with...

Solid-State Synthesis and Characterization of σ-Alkane Complexes, [Rh(L2)(η2,η2-C7H12)][BArF4] (L2 = Bidentate Chelating Phosphine)

Abstract: The use of solid/gas and single-crystal to single-crystal synthetic routes is reported for the synthesis and characterization of a number of σ-alkane complexes: [Rh(R2P(CH2)nPR2)(η2,η2-C7H12)][BArF4]; R = Cy, n = 2; R = iPr, n = 2,3; Ar = 3,5-C6H3(CF3)2. These norbornane adducts are formed by simple hydrogenation of the corresponding norbornadiene precursor in the solid state. For R = Cy (n = 2), the resulting complex is remarkably stable (months at 298 K), allowing for full characterization using single-crystal X-ray diffraction. The solid-state structure shows no disorder, and the structural metrics can be accurately determined, while the 1H chemical shifts of the Rh···H–C motif can be determined using solid-state NMR spectroscopy. DFT calculations show that the bonding between the metal fragment and the alkane can be best characterized as a three-center, two-electron interaction, of which σCH → Rh donation is the major component. The other alkane complexes exhibit solid-state 31P NMR data consistent wi...

Infrared spectroscopic studies on the photocatalytic hydrogenation of norbornadiene by Group 6 metal carbonyls. 2. The role of the diene and the characterization of (.eta.4-norbornadiene)(.eta.2-norbornadiene)M(CO)3 complexes

Abstract: UV laser flash photolysis of M(CO){sub 6} and (NBD)M(CO){sub 4} (NBD = norbornadiene) is used to generate, respectively, the intermediates M(CO){sub 5}(s) (s = n-heptane; M = Cr, Mo, and W) and ({eta}{sup 4}-NBD)M(CO){sub 3}(s) fac and mer isomers; M = Mo and W. Fast ({mu}s) time-resolved IR spectroscopy is then used to measure the rates of reaction of these intermediates with species likely to be components of the catalytic hydrogenation mixture (e.g., H{sub 2}, NBD, CO, etc.). The measurements show that, for a particular intermediate, the rates of reaction with H{sub 2} and NBD are quite similar. Thus, in a typical catalytic reaction mixture, intermediates are more likely to react with NBD than H{sub 2}, because the concentration of NBD is considerably higher than that of H{sub 2}. Fourier-transform IR is used to monitor the carbonyl species present in solution during photocatalytic deuteration at room temperature. These include the previously unknown complexes fac- and mer-({eta}{sup 4}-NBD)({eta}{sup 2}-NBD)M(CO){sub 3}. In the case of W, it is shown that accumulation of mer-({eta}{sup 4}-NBD)({eta}{sup 2}-NBD)W(CO){sub 3} in the solution frustrates the catalytic deuteration (as monitored by the {nu}(C-D) IR bands of the deuterated products). Furthermore, there is a striking wavelength dependence inmore » the catalytic efficiency of the W system. mer-({eta}{sup 4}-NBD)({eta}{sup 2}-NBD)W(CO){sub 3} is sufficiently stable for them to have isolated a sample (ca, 90% purity). {sup 13}C NMR data support the identification of the complex.« less

Efficient Colorimetric Anion Detection Based on Positive Allosteric System of Urea-Functionalized Poly(phenylacetylene) Receptor

Abstract: Poly(phenylacetylene) with rationally designed urea groups was demonstrated to be a superior anion receptor possessing both a colorimetric response ability and a positive homotropic allosteric binding mode. The target polymer, poly(phenylacetylene) with [bis(trifluoromethyl)phenyl]urea pendants (poly-1), was synthesized by the stereoselective polymerization with Rh(nbd)BPh4 (nbd = norbornadiene) in high yield. The anion sensing ability of poly-1 was evaluated using the tetra-n-butylammonium (TBA) salts of a series of anions in THF. Upon the addition of anions such as CH3CO2−, C6H5CO2−, F−, Cl−, Br−, NO3−, N3−, and HSO4−, the yellow color of the THF solution of poly-1 immediately turned to a different color depending on the types of anions, indicating the anion recognition capability of poly-1. The 1H NMR titrations of poly-1 by using increasing amounts of CH3CO2− revealed that the colorimetric response of poly-1 was considered to be the direct consequence of the hydrogen-bonding complex formation between ...