Intramolecular complexation

Keepers, J.W. and James, T.L., A theoretical smdy of distance determinations from NMR two-dimensional nuclear Overhauser effect spectra, J. Mag. Resort, 57, 404, 1984. Kemp, W., Organic Spectroscopy, 3rd ed., W.H. Ereeman, New York, 1991. Figueiredo, P. et al., New aspects of anthocyanin complexation intramolecular copigmentation as a means for colour loss Phytochemistry, 41, 301, 1996. 

For reactants having complex intramolecular structure, some coordinates Qk describe the intramolecular degrees of freedom. For solutions in which the motion of the molecules is not described by small vibrations, the coordinates Qk describe the effective oscillators corresponding to collective excitations in the medium. Summation rules have been derived which enable us to relate the characteristics of the effective oscillators with the dielectric properties of the fi edium.5... 

Oppolzer, W. Transition Metal Allyl Complexes Intramolecular Alkene and Alkyne Insertions. In Comprehensive Organometallic Chemistry II Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds. Elsevier Oxford, 1995 Vol. 12, pp 905-921. 

Figueiredo, P. et al., New aspects of anthocyanin complexation. Intramolecular copigmentation as a means for colour loss Phytochemistry, 41, 301, 1996. 

The crown ether 11 has a trimethylammonium group reaching into the interior of the cavity and is complexed intramolecularly by short CH—O hydrogen bonds. Additional hydrogen bonds between the acidified CH3 groups and the iodide anion were confirmed by X-ray analysis. 

In the case of the anionic manganese complexes, subsequent protonation affords the neutral alkylcarbene complexes. Intramolecular addition of deprotonated dppe to the a-carbon occurs on reaction of [Fe(=C=CMe2XdppeX C5H5)J+ with base [NaN(SiMe3)2 or KOH in tet-... 

Instead of solvent complexation, intramolecular chelation can also stabilize germanium-centered anions. Aryl(8-methoxy-l-naphthyl)hydrogermyllithiums, prepared from the corresponding chelated organogermane in 50-90% yield, are stable and their spectroscopic characteristics suggest a double-metal complexed structure (equation 7)17. 

Kato et al. (1983) studied PVK containing three different intramolecular charge-transfer complexes, each containing a carbazole donor chromophore and a tricyanovinyl acceptor. The results were compared to PVK TNF and PVKiTCNE (telracyanoethylene) intermolecular complexes. Relative to the intermolecular complexes, intramolecular complexes show high primary quantum yields. The thermalization distances were about 22 A, less than 28 to 35 A for the intermolecular complexes. Differences in the structure of the intramolecular complexes caused slight differences in the primary quantum yield, but did not cause significant differences in the thermalization distance. 

Hydride abstraction from dienyl tricarbonyl iron complexes furnishes cationic dienyl tricarbonyl iron complexes. For example, reaction of the diene-iron tricarbonyl complex (115) with triphenyhnethyl hexafluorophosphate followed by trimethylsilyl cyanide furnished with excellent regio- and stereoselectivity a new diene iron tricarbonyl complex (116) (Scheme 170). Excellent regio- and stereoselectivity is seen upon reaction of the cationic complex (116) with trimethylsilyl cyanide (TMS-CN) (Scheme 170). Reduction of the nitrile affords a spirocyclic lactam complex. Intramolecular cyclization of in situ formed enols furnishes spirocyclic compounds again with excellent stereoconfrol (Scheme 171). An interesting example of hydride transfer from a cyclohexadiene ring to a pendant aldehyde followed by nucleophilic addition is seen in Scheme 172. 

Diels-Alder Reactions. Chiral a,p-unsaturated imides participate in Lewis acid-promoted Diels-Alder cycloaddition reactions to afford products in uniformly excellent endo/exo and endo diastereoselectivities (eq 50 and 51). Unfortunately, this reaction does not extend to certain dienophiles, including methacryloyl imides, p,3-dimethylacryloyl imides, or alkynic imides. Cycloadditions also occur with less reactive acyclic dienes with high diastereoselectivity (eq 52). Of the auxiliaries surveyed, the phenylalanine-derived oxazolidinones provided the highest diastereoselectivities. This methodology has been recently extended to complex intramolecular processes (eq 53). In this case, use of the unsubstituted achiral oxazolidinone favored the undesired diastereomer. 

A more complex intramolecular hydrogen bond system is built in the platinum(II) complex 33 (O Fig. 8) in which the central f/trco-configured diol is the chelation site. A y and a S hydrogen bond, each starting at one of the terminal donor hydroxyl functions, end at one and the same alkoxido function. The other one is an acceptor in a more strained p hydrogen bond [22]. Affirmed by DPT calculations, the completion of an octahedral coordination sphere of trimethyl-platinum(n) in a dinuclear complex is accomplished with facial tridentately bonded D-mannitol (coordination mode , 0, 0 k 0, 0, 0 ) [38]. 

Naltrexone (1) has a 14-OH group in addition to the 4,5-epoxymorphinan structure, which comprises four sequential asymmetric centers with two OH groups, and a basic nitrogen. This structure has led to many complex intramolecular reactions. In fact, in 1989 and 1990, we showed that the 14-OH group participated in several characteristic intramolecular reactions [13, 14]. 

A second, less used, strategy encompasses the Lewis acid catalyzed intramolecular reaction of a silyl enol ether with a propargyl cation. The latter can be conveniently generated by a cobalt complexed propargyl ether. This complexation strongly helps the carbocation formation. By using cobalt complexation, intramolecular aldol type reactions (for R = OR ) have been accomplished. ... 

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