Asymmetric norbomadiene

Norbomanol with 96% ee was obtained by the asymmetric hydrosilylation of norbomene. Monofunctionalization of norbomadiene (565) was achieved with high chemo- and enantioselectivities to give uro-2-trich 1 orosilyl-5-norbornene (566) with one equivalent of trichlorosilane and converted to the alcohol 567 with 95% ee. With 2.5 equivalents, the chiral disilylnorbomane 568 was obtained rather than the me so isomer 569 (18 1). The disilylated product 568 was converted to the diol 570 with 99% ee [218],... 

The quadricyclane-1-carboxylate /norbomadiene-2-carboxylate 49/48 seems to be the only asymmetric isomerization studied successfully [106,117]. We tried the isomerization of 3-(l-methylpropyl)azobenzene with cpl, but no CD effect appeared. 

The reaction of the polymeric diene complexes, [RuCl2(diene)]u [diene = cod (1,5-cydooctadiene), nbd (2,5-norbomadiene)], with allylic Grignard reagents gives white bis(allylic) complexes, Ru(allyl)2(diene) (allyl = C3H5, 2-methylallyl), which contain asymmetrically bonded allyl ligands (Eq. 5.2) [10],... 

Asymmetric hydrocyanation has now been achieved using norbomene and norbomadiene as substrates. The reduction of either [PdCl2(+)-DIOP] or PdCl2 in presence of (-I )-DIOP led to a palladium(O) species formulated simply as [Pd(-l-)-DIOP]. This gave, in reaction (164), an optical yield of 30% for the 2-cxo-cyanonorbornane formed. Norbomadiene with the same catalyst gave 2-cxo-cyanonorborn-5-ene with an optical purity of 17%. When the ligand CHIRAPHOS (51) was used, the catalytic activity was greatly diminished. In addition to the review of the early work already mentioned, two more recent reviews of hydrocyanation have appeared. ... 

Dichloro((/ )-N//-dimethyl-l-[(S)-2-(diphenylphosphino)ferrocenyl]ethylamine) palladium(II), [(R)-(5)-PPFA]PdCl2, is an efficient catalyst for the asymmetric hydrosilylation of styrene and norbomadiene with HSiCl3, which gives rise to (S)-a-phenyl-ethyltrichlorosilane and (lR,25,45)-norbomyltrichlorosilane, respectively, in good yields ... 

N-acyldehydrodipeptides were readily prepared either by the condensation of N -acyldehydro-a-amino acids with a-amino acid esters or by the reaction of the azlactones of dehydro-a-amino acid with a-amino acid esters (eq. 1). Asymmetric hydrogenation of the N-acyldehydrodipeptides thus obtained (eq. 2) was carried out by using rhodium complexes with a variety of chiral diphosphines such as -Br-Phenyl-CAPP (3), Ph-CAPP (3), (-)BPPM (4), (+)BPPM (4), (-)DIOP ( ), (+)DIOP ( ), diPAMP (6), Chiraphos (7), Prophos (S), BPPFA (9) and CBZ-Phe-PPM (Fig. 1)(10). The chiral catalysts were prepared in situ from chiral diphosphine ligand with [Rh(NBD)2l -CIO4 (NBD = norbomadiene). Typical results are summarized in Tables I-V. 

Investigations aimed at finding new and easily accessible ligands for asymmetric transformations are an active area of research. It is widely known that chelating dienes such as 1-5-cycIooctadiene (cod) and norbomadiene (nbd) are stable ligands for late transition metal complexes, but use of their chiral versions has not been widely explored. Hayashi et and Defieber et have independently... 

Use of a monosubstituted acetylenes, such as phenylacetylene, in the homo Diels-Alder reaction results in chiral deltacyclenes, which contain a total of 6 asymmetric carbon atoms. However, as a consequence of the two and only two different addition modes of a monosubstituted acetylene to norbomadiene, the deltacyclene is formed as a pair of enantiomers. 

In this area, the complex Cp RuCl(cod) has shown to be an excellent catalyst for the [2+2] cycloaddition of various internal alkynes with a variety of substituted norbomenes and norbomadienes [69-83]. A number of aspects of this reaction have been studied, notably the reactivity, the chemo- and regioselectivity of tmsymmet-rical substrates [69-73] and the asymmetric induction with chiral auxiliaries on the alkyne partner [74—77] [Eq. (31)]. 

A catalytic asymmetric cycloaddition reaction between norbomadiene and methylenecyclopropane can also be achieved in the presence of a [Ni(cod)2]-(—)-benzylmethylphenylphosphine catalyst to give the cycloadduct (72) in an optically active form. This reaction may proceed via a metallocyclopentane intermediate. The reactions of methylenecyclopropane with [Ni(cod)2l-phosphine systems do not appear to involve cleavage of the three-membered ring. However, the bis(acrylonitrile)nickel-catalysed cycloaddition reaction of methylenecyclopropane with methyl acrylate, which yields 3-methoxy-carbonylmethylenecyclopentane (73), does involve C—C bond cleavage. Reaction with the deuterium-substituted compound CHD=CDC02Me gives the cyclopentane derivative (74). An intermediate of the type (75) may be involved in this reaction. 

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