Isocyanide derivatives

In summary, [Au(alkynyl)(CNR)j complexes also show mesomorphic behavior but, in contrast to the halide-isocyanide derivatives, they are thermally less stable and usually decompose before or at the clearing temperatures. This thermal instability is thought to be associated with the gold-(alkynyl) bond and makes these compounds... 

Sheehan and coworkers [47] have also prepared a novel isocyanide derivative, which was used in an Ugi-4CR to prepare noncovalent inhibitors of factor Xa, a key element in the coagulation process [48]. 

The addition of CF3CH2NC or CH2FCH2NC to [Ru(TPP)(CO)] yields [Ru(TPP)(CF3CH2NC)2] or [Ru(TPP)(CFCH2CH2NC)2] respectively. and F NMR spectroscopic data for these and the corresponding alkyl isocyanide derivatives suggest similarities in the bonding properties of members of this family of compounds. 

Fig. 4 Synthesis of heterocycles through intramolecular nucleophilic displacement of the isocyanide derived group...

Fig. 5 Post-Ugi cyclization driven by nucleophilic afkyl substitutions where the isocyanide-derived amide serves as nucleophile...

Another electrophile that can interact with the isocyanide-derived amide is an aldehyde. However, an additional carbonyl function cannot be introduced as such into one of the components without interfering with the Ugi process. Thus it is better used in masked form as an acetal (Fig. 9). Starting from amine 49 a series of oxopiperazines 51 has been prepared, also on solid phase [66],... 

Alternatively, the acidity of the aldehyde-derived CH or CH2 group can be enhanced by converting the isocyanide derived amide into an ester. According to this principle, tandem Ugi-Dieckmann was exploited in the context of carbapenem synthesis, where the first 4-membered ring was built through an intramolecular Ugi reaction of p-amino acid 66. Then, after a three-step manipulation of the carboxylic appendages, a Dieckmann cyclization afforded, stereoselectively, the desired carbapenem skeleton 67 [79]. 

We have previously seen how cyclic lactams can be synthesized by installing a protected amine in one of the Ugi or Passerini components, followed by cyclization onto the isocyanide-derived amide, taking advantage of the particular reactivity of convertible isocyanides. The same type of compounds can be accessed through nucleophilic attack of the amine onto an ester moiety, suitably installed as additional function into another component. This strategy has been widely used for the preparation of diketopiperazines 104 (Fig. 22), a typical privileged structure, starting with... 

By the same procedure are obtained the corresponding biphenyl isocyanide derivatives (Figure 7.20) [18]. Now, the free isonitriles are already liquid crystals displaying nematic and SmA phases with a short range of existence at moderate temperatures (40-85 °C), while the complexes show a marked increase in the melting points and also an expansion ofthe range of existence of the mesophase (up to 140 °C N and SmA phases). The exception is the shortest iodo-derivative, which is not a mesogen. Most of the complexes decompose into the isotropic state (above 220 °C). The biphenyl moiety increases the polarizability anisotropy compared to the phenyl and hence facilitates liquid crystal behavior. 

The pure benzoyl isocyanide derivative is Anally obtained as red crystals (1.40-2.23 g, 50-80% yield, mp 78 °C) following thin-layer chromatography (TLC) on silica gel plates (40 x 20 cm) in a large developing tank (43 x 23 x 29cm) using 700 mL of (C2H5)20-petroleum ether (1 4) as eluent. The desired product is contained in the red band on the TLC plate. 

Treatment of the iron carbene Fe(tetraphenylporphyrinXCCl2) with primary amines provided a novel route to the isocyanide derivatives Fe(tetra-phenylporphyrin)(NH2R)(CNR) (R = Pr1, Bu", Bu ) (96). 

There are few other examples of complete substitution of carbonyl groups from a homoleptic metal-carbonyl complex by isocyanide ligands [cf. Ni(CO)4 (24), Fe(CO)s (26), and Mo(CO)6 (124)]. The corresponding butyl isocyanide derivative Co CNBuOg was formed by reduction of [Co(CNBu )5]PF6 with potassium amalgam (19). 

The rhodium binding energy is 0.5 eV higher in the case of the bis-isocyanide derivative. This is in favor of the effective ji back donation from metal to ligand that is also reflected by the energy of the isocyanide stretching vibration in the IR spectrum of the complex. 

P1 = NH2 protected amino acid or peptide, P2-NC = isocyanide derived from C02H protected amino acid or peptide, P3-NH2 = C02H protected amino acid or peptide ... 

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