Norbornadiene

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

Synthesis and reactivity of a zirconocene bis-(aminoborylphosphane)

Abstract: The reaction of Cp2ZrCl2 with LiP(H)B(Ni-Pr2)2 • DME in a 1 : 2 ratio provides the metallodiphosphane Cp2Zr(P(H)B(Ni-Pr2)2)2 (5) Combination of 5 with Mo(CO)4(norbornadiene) gives the diphosphane adduct Cp2Zr(P(H)B (Ni-Pr2)2)2Mo(CO)4 (7) in which 5 acts as a bidentate chelating ligand The reaction of 5 with n-BuLi in a 1 : 1 ratio generates a phosphane-phosphide "ate" complex Li{Cp2Zr(P(H)B(Ni-Pr2)2)(PB(Ni-Pr2)2)} • DME (8) This unusual complex contains a planar, asymmetric ZrPLiP ring The compounds have been characterized by spectroscopic methods and the molecular structures of 7 and 8 have been determined by X-ray diffraction methods

Design of Improved Molecular Solar‐Thermal Systems by Mechanochemistry: The Case of Azobenzene

Abstract: Molecular solar‐thermal systems (MOST) have emerged in these last years as a novel concept to store solar light. They rely on two state molecular switches that can absorb a photon to convert the initial state A to a higher‐in‐energy state B. The chemical energy stored by B can be then released to reconstitute A. Although simple in its principle, an optimal MOST needs to satisfy several requirements: incoming photon energy in the solar spectrum range, high photoreaction quantum yield, high storage density, no degradation. The first challenge is therefore the search for molecular switches that accomplish all such properties. Until now, trial‐and‐error experiments have been performed, led by physicochemical intuition. The result is that most of the initially proposed switches have been abandoned in favor of the preferred norbornadiene/quadricyclane system, together with its derivatives. Nevertheless, most of the solar spectrum is still out of the MOST absorption region, hence requiring novel approaches. Here, it is shown how mechanochemistry can be applied to improve the principally desired characteristics of a MOST: photon absorption energy, storage energy, and thermal B‐to‐A energy barrier. It is especially shown how azobenzene—a paradigmatic photoswitch still attracting much attention—can be proposed, within certain limits, as a MOST when applying external forces.

Formation of polycyclic hydrocarbons containing a spiropentane or methylenecyclobutane moiety upon thermal decomposition of cyclopropane-containing 1- pyrazolines

Abstract: 1-Pyrazolines1 and2 obtained by 1,3-dipolar cycloaddition of diazocyclopropane to norbornene or deltacyclene undergo dediazotization at 410–450°C to give a mixture of strained hydrocarbons, namely, spirocyclopropane-1,3'-tricyclo[3.2.1.02,4]octane (4) or spiro{cyclopropane-1,4'-pentacyclo[4.4.0.02,8.03,5.07,9]decane} (6) and isomeric tricyclo[5.2.1.02,5]dec-5-enes (5) or pentacyclo[6.4.0.02,10.03,6.09,11]dec-6-enes (7) in a 30–70% overall yield. An increase in temperature favors the isomerization of spiro hydrocarbons4 and6 to the respective unsaturated hydrocarbons5 and7. The latter undergo cyclopropanation with diazomethane in the presence of Pd(acac)2 or (PhO)3P · CuCl to afford polycyclanes9a,b or10a,b containing a spiro[2.3]hexane moiety condensed at thecis-1,4 position. Unsaturated 1-pyrazoline3 obtained from diazocyclopropane and norbornadiene decomposes at 330–370°C with elimination of cyclopentadiene to give 3(5)-vinylpyrazole in a yield up to 75%.

Donor–acceptor accelerated norbornadiene rearrangements

Abstract: The norbornadienone acetals 3 with a CO2Me, CONMe2 or CHO substituent at C-2 undergo rearrangement under very mild conditions; cycloheptatrienes are obtained for CO2Me and CONMe2 substituents and the furanone acetal 9 for the CHO substituent. The donor-acceptor acceleration is consistent with a formal 1,3-shift to a norcaradiene proceeding either via a zwitterionic intermediate or a concerted-forbidden path. Rearrangement via a biradical is not consistent with the slower rearrangement of 7-cyano-7-methoxy-2,3-bis(methoxycarbonyl)norbornadiene 16. The indene 19 racemises rapidly at a temperature 100 °C below that required for 18 establishing that a donor and an acceptor (Me3SiO and CN) at a potential radical centre promote homolysis to a greater extent than two donor groups (two alkoxy groups).

Process for preparing ring opening polymers

Abstract: PURPOSE:To prepare ring opening polymers of norbornene derivatives or norbornadiene dirivatives with high yields, by applying specific highly active catalysts.