Porphyrin binaphthyl

Collman et al.99 reported the asymmetric epoxidation of terminal olefins catalyzed by iron porphyrin complex 129. The catalyst was synthesized by connecting binaphthyl moieties to a readily available aa/ / -tetrakis(aminophenyl)-porphyrin (TAPP). Epoxidation of unfunctinalized olefins was carried out using iodosylbenzene as the oxidant. As shown in Scheme 4-46, excellent results were... 

The conjugation in the molecular wire may be disrupted or modulated to create systems with different properties. For example, a porphyrin Ceo donor-acceptor system linked with a conjugated binaphthyl unit, has a preference for the atropi-somer where the fullerene unit is closer to the porphyrin system, thus increasing the through space interactions [82]. The charge transfer process on a dyad containing a crown ether in the linker structure can be modulated by complexation/ decomplexation of sodium cations [83] but even more interesting is the construction of supramolecular systems where the donor and acceptor moieties are... 

Callot and co-workers established in 1982 that iodorhodium(III) porphyrin complexes could be used as cyclopropanation catalysts with diazo esters and alkenes with c/.s-disubstituted alkenes these catalysts provide preferential production of cis(syn) disubsdtutcd cyclopropancs (syn/anti up to 3.3 with 1,4-cyclohexadiene) [72], More recently, chiral porphyrins have been designed and prepared by Kodadek and co-workers [73], and their iodorhodium(lll) complexes have been examined for asymmetric induction in catalytic cyclopropanation reactions [74,751. The intent here has been to affix chiral attachments onto the four porphyrin positions that are occupied in tetraphenylporphyrin by a phenyl group. Iodorhodium(III) catalysts with chiral binaphthyl (27, called chiral wall porphyrin [74]) and the structurally analogous chiral pyrenyl-naphthyl (28,... 

Compound 2 was furthermore employed in the preparation of NH-linked Pc-porphyrin arrays [60]. The reaction between the amino-functionalized porphyrin 8 and 4-iodophthalonitrile using Buchwald-Hartwig amination conditions (Pd(OAc)2/ rac-BINAP (BINAP = 2,2/-bis(diphenylphosphino)-l,l/-binaphthyl) as the catalytic system) in the presence of potassium fe/7-butoxide, delivered the entities connected either at the meso-phenyl group (9 in Fig. 7) or at the /1-pyrrolic position [61]. 

Chiral binaphthyl-bridged mevo-tetrakis(2-aminophenyl)porphyrin]cobalt or polymer-supported chiral (salen)Co complexes also catalyzed the cyclopropanation of styrenes albeit so far with lower diastereo- and enantioselectivities [363, 364],... 

Rose, E., Ren, Q.-z., Andrioletti, B. A unique binaphthyl strapped iron-porphyrin catalyst for the enantioselective epoxidation of terminal olefins. Chem.-Eur. J. 2004, 10, 224-230. 

Naruta et al. [225, 226] designed the twin-coronet porphyrin ligands (62) and (63) with binaphthyl derivatives as chiral substituents (Figure 13). Each face of the macrocycle is occupied by two binaphthyl units and the ligand has C2 symmetry. Iron complexes of these compounds can be very effective catalysts in the epoxidation of electron-deficient alkenes. Thus, nitro-substituted styrenes are readily epoxidized in 76-96% ee [226]. The degree of enantioselectivity can be explained on the basis of electronic interactions between the substrate aromatic ring and the chiral substituents rather than on the basis of steric interactions. 

Iodorhodium(IIl) porphyrins also efficiently catalyze the reaction of ethyl diazoacetate with simple alkenes. generally providing the cw-isomers as the major product77 79110. The cis( tram ratio increases when bulkier porphyrins, such as tetramesitylporphyrin (TMP), are employed. The mechanism of this rhodium-catalyzed cyclopropanation with diazoacetate is interpreted as proceeding via carbene complexes79 80 111,112. Based on these results, asymmetric cyclopropanation of alkenes with ethyl diazoacetate is achieved if catalyzed by a chiral wall porphyrin81. An earlier described binaphthyl-system of this type82113114, introduced as an iodorhodium(lll) complex, 6, forms an extremely active catalyst and leads to m-cyclopropanes (preferred over the rran.v-products) with moderate to poor enantioselectivities if styrene, 1- and 3-phenylpropene are used as substrates (10-60% ee)81. 

Figure 1.3. Catalyic asymmetric hydroxylation by a chiral, binaphthyl porphyrin. The stereochemical outcome of a hydroxylation depends upon the steric fit of the substrate.

Collman et al. reported a series of picket basket porphyrins (Figure 1.14) which show extremely high shape selectivity (>1,000 for cis-2-octene vs cw-cyclooctene) and relatively high enantioselectivity in olefin epoxidation (ee around 70-85%) Chiral, binaphthyl straps between adjacent o-aminophenyl groups have afforded very good enantiomeric selectivities for styrene epoxidations. ... 

The first use of a chiral porphyrin to carry out asymmetric epoxidation was reported in 1983, giving 50% ee with jn-chlorostyrene . The ee was improved to 70% for epoxidation of cis-3-methylstyrene with the use of a very robust chiral vaulted binaphthyl porphyrin 16 (Figure 1.15) . More significantly, this catalyst afforded the first case of catal5rtic asyitunetric hydroxylation by a model system, giving a 70% ee for hydroxylation of ethylbenzene and related hydrocarbons . 

Further developments of this system have led to studies of the binaphthyl-peptide-strapped porphyrin 17". For styrene epoxidation this chiral catalyst afforded an ee greater than 90% in the initial stages of the reaction, with the (/f)-styrene oxide predominating. NMR Tj relaxation studies with the copper(ll) derivative of the same ligand... 

The use of inorganic supramolecular compounds in catalysis has also been successful in recent years. Hupp etal. incorporated a Mn (III)-porphyrin see Porphyrin) epoxidation catalyst inside a molecular square, a system that shows enhanced catalyst stability and substrate selectivity as compared to the free catalyst. In another example, chiral metallocyclophanes were constructed from Pt(PEt3)2 units and enantiopure atropoisomeric l,E-binapthyT6,6 -bis-(acetylenes) and used in enantioselective diethyl zinc addition to aldehydes to afford chiral secondary alcohols. The first organometallic triangle based on Pt(II) and alkyne-di-substituted-binaphthyl system was reported and found to effect asymmetric catalysis reactions of aldehydes to alcohols with excellent conversion rates and enantiomeric excess/ ... 

Fig. 7.24 Synthetic porphyrins that model cytochrome P450s (a) protection of metal centre from oxidation (b) shape and regioselectivity and (c) asymmetric induction. [After Gunter and Turner.] In (c) the space-filling shapes represent binaphthyl units.

Catalytic asymmetric C-H oxidation has also been achieved using metal porphyrins and metal(salen) complexes. Benzylic oxidations using vaulted binaphthyl iron(III) porphyrins,and manganese(III)(salen) complexes have suffered from moderate yields and/or enantioselectivities. However, Miyafuji and Katsuki have obtained reasonable yield and good enantioselectivity for C-H... 

Figure 16 l,l -Binaphthyl-substituted macrocycles as receptors for saccharide recognition based on the idea of a picket-fence porphyrin. 

The versatility of the Meyers reaction for the construction of the dibenzocyclooctadiene backbone is amply documented (Fig. 8.2). In particular, lignans (-)-interiotherin A (17) [21], (-)-schizandrin (18), (-)-isoschizandrin (19) [22], and (-)-gomisin E (20) [21] were prepared by this method. The synthetic utility of the Meyers reaction to create the axially chiral biaryl skeletal framework was further displayed by the atroposelective syntheses of natural naphthylisoquinoline alkaloids including (-)-O-methylancistrocladine (21) [23] and (-)-0-methylhamatine (22) [24], among others [25, 26], and by the synthesis of enantiomericaUy pure C -symmetric biphenyl ligand 23 and binaphthyl porphyrin 24 (Fig. 8.3), which have been used as intermediates for the preparation of chiral catalysts for asymmetric reduction and epoxidation [27, 28]. 

Non-porphyrin ruthenium complexes such as [RuCl(DPPP)2] (DPPP = l,3-bis (diphenylphosphino)propane), [Ru(6,6-Cl2bpy)2(H20)2], binaphthyl-mthenium complex, and RUCI3 catalyze oxidations of alkenes with PhIO [45], t-BuOOH [46], PhI(OAc)2 [47], or H2O2 [48] to give the corresponding epoxides in moderate yields. 

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