Hetero bridges

Molecular modelling (AMI) indicated that the bridge hetero-atom separations in 137 were as follows N-N = 8A, N-0 = 4.6A, 0-0 = 2.7 A. In addition, the invertomer preference of the N-benzyl groups position them over the aromatic rings thereby ensuring that the lone pairs on the heteroatoms are concentrated within the cavity section of the molecule. 

Scheme 6 Reaction Scheme for the Formation of a Disulfide-Bridged Hetero-Two-Stranded a-Helical Coiled...

Another early-late bimetallic complex related to the (71) group can be prepared by connecting the two Cp rings by a carbon bridge. Its reaction with an excess of AlMes affords a doubly bridged hetero bimetallic complex (equation 34). ... 

The bridged hetero[ll]annulenes (120) have been obtained as shown. Evidence from their n.m.r. spectra suggests that they exist in the jy -form (121). The bright red thienocyclobutadiene (122) was obtained as shown. Among other heteroannulenes synthesized using Wittig olefin syntheses are a thia[ll]annulene, an oxa[13]annulene, the oxa[15]annulene... 

Dicarbonyl Compoonds.—Wittig reactions of cycloheptatriene-1,6-dialdehyde to form bridged hetero[ll]annulenes are discussed. The kinetics of formation of the cyclic adduct between cyclodecane-1,2-dione and trimethyl phosphite have been discussed. ... 

Application of solvento-complexes in the synthesis of bridged hetero- and homopolynudear complexes... 

Solvent molecules are typically weak donors and can be replaced readily by other ligands. In most cases, these substitution reactions proceed so easily that solvento-complexes can often be considered as coordinatively unsaturated intermediates. However, the importance in synthesis of solvento-complexes is dramatically illustrated by substitution reactions employed in the synthesis of bridged hetero- and homopolynudear coordination compounds. 

Heteroannulenes electrophilic reactions, 7, 726 tr-excessive synthesis, 7, 727 nucleophilic reactions, 7, 727 Hetero[l IJannulenes structure, 7, 715 Hetero[ 12]annulenes pyridine-like methano-bridged, 7, 715 Hetero[ 13]annulenes unrestricted structure, 7, 716... 

Progress in molecular recognition of functionalized calixarenes with hetero-atomic bridges as synthetic receptors 99MI43. 

Gaseous chloride complexes with halogen bridges — homo-complexes and hetero-complexes. 

Warrener RN (2000) New adventures in the synthesis of hetero-bridged ryn-facially fused nomomadines ( n]polynorbomadienes ) and their topological diversity. Eur J Org Chem 2000 3363-3380... 

While essentially all the metal carbonyl complexes for group 4B contain terminal CO ligands, only recently have some bonafide doubly bridging carbonyl complexes been reported. However, these complexes are hetero-nuclear, since the carbonyl ligand bridges a zirconium atom with the metal center of a late transition metal. 

Finally, it is important to mention that there are other related publications in which porphyrin macrocycles are not directly used as dipolarophiles but are transformed into new derivatives that can react with carbonyl ylides via ACE (alkene cyclobutene epoxide) reactions. This idea arose in 1997, when Russell and co-workers found that fused ester-activated cyclobutene epoxides 86 can be ring-opened to give carbonyl ylides 87, and that these can be trapped stereospecifically by ring-strained alicyclic dipolarophiles, such as 2,5-norbomadiene, to form hetero-bridged norbomanes 88 in good yields, through ACE transformations (Scheme 31) <97CC1023>. 

Several years later, Kanatzidis et al. reported the preparation of hetero-binuclear complexes of tetrahedrally arranged Cu and In centers, with two bridging thiolato or selenolato groups, [ PPh3 2Cu(p-QEt)2In(SEt)2], (Q = S or Se) (i.e., equation 6.3).38 Pyrolysis studies undertaken revealed that the Se derivative could be converted into CuInSe2 at 400-450 °C at 0.01 mm Hg (see equation 6.4). However, none of the precursors had been evaluated in a thin-film deposition study. 

The synthesis of multivalent neoglycoconjugates by 1,3-dipolar cycloaddition of nitrile oxides and alkynes has been reported (493). The nitrile oxides have been generated in situ in the presence of alkynyl derivatives, allowing the access to homo and hetero multivalent systems containig O- and C-linked glycosides and isoxazole bridges. 

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