Norbornadiene addition

Table 3. Products of Addition of Halogen Fluorides to Norbornadiene...

The phosphonium salt method works best with nucleophilic olefins [//, 12, 16, 17, 18, 19] (Table 1 and equations 1-3) and has been used m mechanistically important studies of difluorocarbene additions to norbornadienes [20 21, 22, 23] that provided the first example of a concerted homo-l,4-addition (equation 4) A recent modification uses catalytic 1,4,7,10,13,16 hexaoxacyclooctadecane (18-crown-6) to shorten reaction times and increase yields with less nucleophilic olefins [12] (Table 1) Neither procedure, however, compares with the use of phenyl(tri-f1uoromethyl)mercury or (trifluoromethyl)trimethyltin reagents [efficient reactions with less nucleophilic olefins (equations 3 and 5) and cyclic dienes [24, 25] (equations 6 and 7)... 

In a manner analogous to classic nitrile iinines, the additions of trifluoro-methylacetonitrile phenylimine occur regiospecifically with activated terminal alkenes but less selectively with alkynes [39], The nitnle imine reacts with both dimethyl fumarate and dimethyl maleate m moderate yields to give exclusively the trans product, presumably via epimenzation of the labile H at position 4 [40] (equation 42) The nitrile imine exhibits exo selectivities in its reactions with norbornene and norbornadiene, which are similar to those seen for the nitrile oxide [37], and even greater reactivity with enolates than that of the nitnle oxide [38, 41], Reactions of trifluoroacetomtrile phenyl imine with isocyanates, isothiocyanates, and carbodiimides are also reported [42]... 

The diphosphadithiatetrazocines 13.2 (E = S) and 13.3 (E = S) contain one more R2PN unit in the ring than 13.1. The structure of the orange-red 1,3-isomer (13.2, E = S, R = Ph) consists of an essentially planar N3S2 unit with the two phosphorus atoms located on opposite sides of the plane." Like 13.1 this isomer forms a 1 1 adduct with norbornadiene via 1,3-addition across the sulfur atoms. 

When the diepoxide of norbornadien-7-one is passed through a hot capillary tube with nitrogen, a small amount (20 %) of oxepin is formed in addition to 4,5-epoxy-4,5-dihydrooxepin... 

Edman and Simmons [146] synthesized bicyclo[2.2.1]hepta-2,5-diene-2,3-dicar-boxylic anhydride 80 as a facially perturbed dienophile on the basis of the norbornadiene motif, and its top selectivity in Diels-Alder reactions with cyclopentadiene (top-exo top-endo = 60 70 1) was observed by Bartlett (Fig. 14) [147], The most preferred addition was top-exo addition, along with the minor addition modes, top-endo bottom-enrfo addition (Fig. 14). The addition of butadiene to this anhydride preferentially afforded the top-adduct (top bottom = 6 1). In the addition of anthracene, a top-adduct was formed exclusively. 

Cycloaddition of bicyclo[2.2.1]hept-2-ene-2,3-dicarboxylic anhydride 81 with cyclopentadiene was also studied by Bartlett et al., who found exclusive top addition, the top-endo/top-exo ratio being 3 2 [147]. The endolexo ratio is significantly different from that of 80 (60-70 1). The observed top selectivity in norbornadiene (80) and norbomene (81) derivatives is consistent with the inherent top reactivity of norbomanone 25 and norbomene 57. Orbital unsymmetrization of the dienophile... 

Formation of mixtures of products in these reactions can be attributed largely to the properties of the acetate group. The reactions of a number of cycloalkenes with thallium(III) salts have been investigated in some detail and the results obtained have served both to elucidate the stereochemistry of oxythallation and to underline the important role assumed by the anion of the metal salt in these oxidations. The most unambiguous evidence as to the stereochemistry of oxythallation comes from studies by Winstein on the oxythallation of norbornene (VII) and norbornadiene (VIII) with thal-lium(III) acetate in chloroform, in which the adducts (IX) and (X) could be precipitated from the reaction mixture by addition of pentane 128) (Scheme 11). Both by chemical means and by analogy with the oxymercuration... 

In a series of experiments using various pressures of CO and H 0, with norbornadiene as the diene /44, 45/, we were able to verify an earlier suggestion /43/ that the 1,2 addition product norbornene is formed through a diene dissociation (Equation 43) and the 1,5 addition product nortricyclene through a CO dissociation (Equation 42). 

A wide range of catalysts is now known that will bring about B H addition to simple terminal alkenes. For group 9 complexes, catalytic activity follows the order [(dppe)Rh (nbd)]+ > [Rh(PPh3)3Cl] > [(COD)Ir(PCy3)(C5H5N)]+ (where dppe = 2-bis(diphenylphosphino) ethane and nbd = norbornadiene).19 Different facial selectivity is found for catalytic hydroboration reactions of these compounds with chiral alkenes (Equation (1)). Thus, [(dppe)Rh(nbd)]+ gives... 

As in the case of dimerizations, MCP derivatives are known to undergo metal-catalysed [2 + 2] codimerizations with other alkenes in a few cases [2]. The examples are limited to strained olefins, such as norbornadiene (572) (Scheme 79) [152] and cyclobutene (574) (Scheme 80) [153], and to alkyl acrylates (Table 46) [154] and always compete with the alternative [3 + 2] addition of TMM species. 

The reaction of acyclic ADC compounds with monoenes has already been discussed in Sections III,B and IV,B. In certain cases the major reaction pathway involves addition of the ADC compound as a 47r component, to the monoene to give 1,3,4-oxadiazines (Scheme 1). 1,3,4-Oxadiazines are the major or sole products from the reactions of ADC compounds with indene,80 and 4-nitrophenyl vinyl ether,90 and from the reaction of azodibenzoyl with enamines and enol ethers.91 93 Norbornadiene also gives a 1,3,4-oxadiazine (42) with ADC compounds.82 However, benzonorbornadiene behaves differently, and the major product from the reaction with PTAD has the structure 119.205 Other bicyclic monoenes react similarly.206 1,3,4-... 

Starting from the Ni mrao-formyloctaethylporphyrin oxime complex, the meso-cyanooctaethylporphyrin N-oxide complex has been synthesized for the first time. The double addition of the nitrile oxide to 2,5-norbornadiene afford a porphyrin dimer, whose structure has been established by X-ray diffraction analysis (485). The 1,3-dipolar cycloaddition reaction of w< .so-tetraarylporphyrins with 2,6-dichlorobenzonitrile oxide yields isoxazoline-fused chlorins and stereoiso-metric bacteriochlorins. The crystal structure of one of bacteriochlorins has been characterized by X-ray diffraction (486, 487). 

It is noteworthy that, at variance with norbornadiene derivatives, the addition of ben-zeneselenenyl chloride to 1,4-cyclohexadienes gives only products of anti 1,2-addition without any jr participation (equations 134 and 135)140. 

In 1991, Park reported123 the first synthesis of iron alkynylcarbene complexes (184), involving the nucleophilic attack of a lithium acetylide on pentacarbonyl iron, followed by electrophilic quench. With such compounds in hand, he proceeded to investigate their reactivity123,124 and found that upon addition of cyclopentadiene to the alkynylcarbene complexes 184, the products formed were 774-vinylketene complexes (185). During column chromatography, some of these products (185.a and 185.b) were transformed into the tricarbonyl(norbornadiene)iron derivatives 186. Others (185.C and 185.d, not shown) were hydrolyzed as part of the workup procedure, to afford pure samples of the norbornadiene complexes 186.C and... 

Nucleophilic olefins react readily with trichloroacetyl isocyanate to give l,3-oxazin-4-ones. In this way, norbornadiene 188 yields the 5,8-methano-2//-l,3-benzoxazin-4-one 189 (69JOC633). A similar 1,4-addition starting... 

The addition of thiobenzoyl isocyanate to norbornene and norbornadiene resulted in the thiazinones 230 (R = Ph) and 231, respectively (67CB685). The ter/-butyl- and mesityl-substituted analogs of 230 were prepared by the same method. In the case of a benzyl substituent, the derivative 232 containing an exo double bond was formed (81CB549). 

A Diels-Alder type of addition (Fig. 4a) can occur through a cobalta-norbornadiene intermediate, followed by reductive elimination, to yield the product and regenerate the cp-Co core (77JA1666). 

Oeeasionally, very good enantioselectivities were achieved in the (-)-sparteine-mediated carbolithiation of 6-dimethylaminofulvene (470) by ort/zo-substituted aiyllithiums 471 (equation 129) . Here, (—)-sparteine (11) turned out the best chiral additive. The lithium cyclopentadienides 472 were converted to the corresponding Rh(l)-norbornadiene complexes 473. 

Scheme 1 ROMP of a 2,3-disubstituted norbornadiene, a 2-substituted norborn-5-ene and polymerization of a 1-alkyne via a- and /3-addition, respectively. A and B are initiator-and termination-derived endgroups, respectively...

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