Reaction of norbornenes

Keywords laser-induced retro-Diels-Alder reactions of norbornene, thermal retro-Diels-Alder reactions of norbornenes and isopropylidenenorbornenes... 

Scheme 6/4.35. Unexpected formation of 6/4-140 by reaction of norbornene and an alkynyl Cr carbene.

It has also been found that the indolizinoquinoline iV-oxidc 291 can be used as a chiral promoter in enantioselective Pauson-Khand reactions in the reaction of norbornene with various alkynes, ee s of up to 33% were obtained in the presence of this promoter <1998H(48)1445>. 

Similar to the addition of secondary phosphine-borane complexes to alkynes described in Scheme 6.137, the same hydrophosphination agents can also be added to alkenes under broadly similar reaction conditions, leading to alkylarylphosphines (Scheme 6.138) [274], Again, the expected anti-Markovnikov addition products were obtained exclusively. In some cases, the additions also proceeded at room temperature, but required much longer reaction times (2 days). Treatment of the phosphine-borane complexes with a chiral alkene such as (-)-/ -pinene led to chiral cyclohexene derivatives through a radical-initiated ring-opening mechanism. In related work, Ackerman and coworkers described microwave-assisted Lewis acid-mediated inter-molecular hydroamination reactions of norbornene [275]. 

Miura reported a 1,4-shift of rhodium in the reaction of norbornene with arylboronic acids (Scheme 3) where rhodium moves from an alkyl sp2-carbon to an aryl sp2-carbon, and the arylrhodium species further reacts with another molecule of norbornene.30 Polyalkylated phenyls are obtained in good yields. Cesium fluoride facilitates the transmetallation, generating the phenylrhodium complex which then coordinates to the -face of norbornene. 

Substituted norbornane derivatives have been synthesized by the reaction of norbornenes with carbonyl ylides derived from a-diazoketones by a 1,3-dipolar cycloaddition route (Equation 97) <2002TL5981>. These reactions occur in high yields and with excellent o o-selectivity (Table 8). 

The reaction of norbornene (5) with xenon difluoride in dichloromethane at various temperatures and in the presence of various catalysts results in the formation of seven products.45 Table 6 shows the significant effect of boron trifluoride-diethyl ether complex as catalyst in the product formation. 

Intermolecular hydroamination or hydroarylation reactions of norbornene and cyclo-hexadiene carried out with catalytic amounts of Brpnsted or Lewis acid in ionic liquids have been found to provide higher selectivity and yields than those performed in classical organic solvents. This effect was attributed to the increases of the acidity of the medium and stabilization of ionic intermediates through the formation of supramolec-ular aggregates with the ionic liquid.38... 

Cycloalkenones.3 Cycloalkenones can be prepared by a retro Diels-Alder reaction of norbornenes of type 1, conducted at 25-70° in the presence of CH3A1C12 (1 equiv.) and a reactive dienophile, usually maleic anhydride or fumaronitrile. The [4 + 2]cycloreversion was used to prepare 12-oxophytodienoic acid (4), which epi-merizes at Cu to the trans-isomer on brief exposure to acid. The precursor nor-bornene 3 was prepared from the known dienone 2 as shown. Treatment of 3 at room... 

The reaction of norbornene (4) with xenon difluoride has been investigated in detail. The acid-catalyzed, liquid-phase fluorination results in the formation of seven products fluoronortricy-clane (30 %), e t/n-2- ii o-5-difluoronorbornane (14%), e.vo-2-f.vp-5-difluoronorbornane (8 %). f jfO-2-c.w-3-difluoronorbornane (2.5%), e c/o-2-e. co-3-difluoronorbornane (1.5%). exo-2-flHfi-7-difluoronorbornane (13%), and t. o-2-.Jvn-7-difluoronorbornane (4%). ... 

The addition of bromine fluoride to cyclohexene occurs highly stereospecifically to yield the fra/i.v-adduct. Further examples of the bromofluorination of cyclic alkcncs with various reagents are reported in Table 21, and also given by the reactions of norbornene benzo-... 

The diastereoselective addition of aniline to norbornene was accomplished using a catalytic amount of iridium(I). As the intermediate azametallacyclobutane 2 could be isolated its stereochemistry was determined by X-ray analysis both iridium and nitrogen occupy the exo position41. However, the scope of the amination method, with respect to the nature of the amine and the structure of the alkene, was not determined. Conversely, the analogous rhodium(I)-cat-alyzed reactions of norbornene and aromatic amines gave mixtures of hydroamination and hydroarylation products106. 

The carbonium ion rearrangements that can be observed in halofluormations are illustrated by the reactions of norbornene (Table 2) and norbornadiene (Table 3). Product ratios may vary with the different reagent combinations... 

Cyclopropane formation can compete with direct conversion of the homoallylmetal complex intermediate. Thus reaction of norbornene (9) with j3-bromostyrene in the presence of tetrakis(triphenylphosphane)palladium(0) and ammonium formate leads to 3-benzyl-la,2j6,3a,4, 5a-tricyclo[3.2.1.0 " ]octane (12 52%) and tra s -2-styrylnorbornane (13 ... 

The following reactions of norbornene and other nonfunctionalized alkenes with substituted methylenecyclopropanes illustrate these points. (1-Methylethylidene)- and (diphenyl-methylene)cyclopropane (1 R = Me, Ph) give rise to the same type of cycloadducts in the presence of either nickel(O) or palladium(O) catalysts. Even at temperatures as low as 40 "C with bis(> -cycloocta-l,5-diene)nickel(0) as catalyst, 2 may be isolated in 70% yield. The reaction can be extended to vinylbenzene and ethene at temperatures of between 40 and 60 °C, where it may be advantageous to use (cyclododeca-l,3,5-triene)nickel(0) ° as a source of the catalytically active nickel(O) species instead of bis(j7" -cycloocta-l,5-diene)nickel(0). ° This is because ligand dissociation from the former complex is more facile, especially at relatively low temperatures. 

Fugami K, Hagiwara S, Oda H, Kosugi M (1998) Novel palladium-catalyzed diarylation and dialkenylation reactions of norbornene derivatives. Synlett 477-478... 

The living ROMP reactions of norbornene and norbornene derivatives have been used to make a variety of polymers possessing unusual properties. Copolymerization of selected functionalized norbornenes with norbornene has been used to synthesize star polymers and side-chain liquid crystal polymers. " This chemistry has also resulted in the preparation of phase separated block copolymers that contain uniform sized metal or semiconductor nanoparticles. The... 

With these possibilities in mind we attempted the photo-oxygenation of norbornene. With either methylene blue or hematoporphyrin as sensitizer and methanol or pyridine as solvent, we obtained no evidence of any reaction by infrared or NMR spectrum, by gas chromatography, or by spot test for hydroperoxide (potassium iodide/starch in 2-propanol/ acetic acid) or peroxide (hydriodic acid/starch in 2-propanol). While the half-life of reaction of cyclohexene was only about one day under our reaction conditions, no evidence of reaction of norbornene was obtained in a period of one month. Assay of norbornene by gas chromatography with benzene as internal standard failed to show any depletion of norbornene over the attempted reaction interval. 

Fig. 18 Reaction of norbornene with the platinum oxo complex 1 yielding the platina-2-oxetane 2. Reproduced with permission from [121]...

The reaction of norbornene with iodobenzene or bromobenzene in the presence of [Pd(PPh3)4] as the catalyst leads to pentacycle 83 (Scheme 11.29) [6, 31, 90-94], This process is known as the Catellani reaction. The parent transformation involves an insertion of the phenylpalladium(II) complex into the double bond of norbornene to give (Ti -phenyl)norbornyl palladium(II) complex 84, which then undergoes intramolecular paUadation to form 85. Further reaction of this paUadacycle with iodobenzene leads to 83. Biphenyl, tetracycle 86, and more complex derivatives 87 and 88, have also been isolated in this reaction [90, 93c, 94], Benzocyclobutenes... 

Using [Rh(CO)2Cl]2 as catalyst, the corresponding trienes have also been shown to undergo the PK-type cycloaddition yielding the products also as single diastereomers (161). However, 1,3-disubstitution on the diene component was not well tolerated for the intramolecular version of the reaction. The intermolecular reaction could be performed as exemplified by the reaction of norbornene 196 and 2,3-dimethyl butadiene 197 under a CO atmosphere (Scheme 89). 

The reaction of norbornene was also found to have a lower activation barrier to form the metallacyclobutane than the reactions of cyclopentene, cycloheptene, and Z-cyclooctene. This can be attributed to the pre-distorted double bond of norbornene, which requires less distortion to achieve the pyramidalized geometry in the transition state than that needed for planar olefins [43]. 

Lima-Neto and Matos [14] have also noted that small amounts of coordinating solvents, such as THF, MeCN, or 2,6-lutidine, could be used as solvent additives for the polymerization reactions of norbornene. In a detailed survey of polymerization reactions with various Ru-based metathesis catalysts, these solvent additives greatly improved the and M IM values. 

Nickel-catalyzed highly chemo-, regio-and stereoselective three component reaction of norbornene with two alkynes. 

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