Mono-isocyanides

These materials are characterized by common techniques such as H NMR, IR, elemental analysis, DSC, and TGA.54 58 59 60 64 68 Other techniques such as electron spin resonance (ESR),54 magnetic susceptibilities54 and Mossbauer spectroscopy (when they apply),56,58 60 64 71 uV-visible spectroscopy,58,59 60 61 64-67 and solid-state electric conductivity measurements5456 59-63 66 67 71 were also employed. These materials were carefully compared to model bis(mono-isocyanide) adducts for better understanding of the physical properties. Important solubility problems are often observed when no alkyl side chain is used. So, these more soluble substituents are incorporated either on the macrocycles or the bridging ligands for better characterization. 

The isocyanide cation [CpFe(CO)(CNMe)2] reacts with pentafluoro-phenyl-lithium to give the cr-aryl complex [CpFe(CNMe)2(C F5)] and the imlne complex CpFe(CO)(CNMe)[C(CeF6) NMe], in which attack at the isocyanide ligand has occurred. The latter complex consists of two isomers, one of which slowly isomerises to the other, which in turn loses carbon monoxide to give CpFe(CNMe),(C F6). With the mono-isocyanide cation [CpFe(CO)j(CNMe)]+, attack occurs on the cyclopentadienyl ring to give... 

The related mono-A/-alkylated carboranes, 7-(NH2R)-7-CB2qH22, can be prepared by treatment of decaborane(14) with alkyl isocyanides (125). 

Van Leusen and Possel described the use of mono-substituted tosylmethyl isocyanides (TosCHRN=C R = alkyl, benzyl, allyl) in the synthesis of 4,5-substituted oxazoles. For example, 4-ethyl-5-phenyloxazole (8) was prepared in 82% yield by refluxing a-tosylpropyl isocyanide (7) and benzaldehyde for 1 hr with 1.5 equivalent of K2CO3 in MeOH. 

Mono-substituted derivatives of [C5HjMn(NO)(CO)2] (32) and di-substituted (20, 146) derivatives of [CH3C5H4Mn(NO)(CO)2] have been prepared by direct reactions of the isocyanide and [C5H5Mn(NO)(CO)2] or [CH3CjH4Mn(NO)(CO)2]. Brunner and Schindler (32) observe variations of vqq and i no for the series [C5H5Mn(NO)(CO)L]+ (L = phosphines, and cyclohexyl isocyanide) in the order CNC H, > P(OPh)3->--->(PPh3)3 > PBuj. Reactions of the mono- and disubstituted complexes with pentafluorophenyllithium (20,146), and of the disubstituted species with borohydride (148) were noted above. 

Bayon, R., Coco, S., Espinet, P., Fernandez-Mayordomo, C. and Martin-Alvarez, J.M. (1997) Liquid-Crystalline Mono- and Dinuclear (Perhalophenyl) gold(l) Isocyanide Complexes. Inorganic Chemistry, 36(11), 2329-2334. 

Mono- and dilithio derivatives of p-tosylmethyl isocyanide 297a were shown to display interesting reactions. Reaction of the monoanion with unsaturated esters was shown to give pyrrole derivatives . Dianion 297b was found to add to the carbon-nitrogen double bonds of isoquinoline, quinoline and quinoxaline affording compounds 298, 299 and 300, respectively. In the reactions with pyridine iV-oxide and pyridazine iV-oxide, unstable open-chain products 301 and 302 were obtained . 

In contrast, stepwise substitution reactions on M(CO)6 (M = Cr, Mo, W) have been achieved with a series of heterogeneous catalysts including co-balt(ll) chloride (27), activated charcoal (159), and platinum metals dispersed on oxide or carbon supports (31), to give mono-, di-, tri-, and complete substitution (124) in yields > 90%. Representative reaction times are given in Table II (159). The efficiency of the method was further demonstrated by the stepwise synthesis of the mixed isocyanide complexes m-Mo(CO)4(CNMe)(CNBu ) and /ac-Mo(CO)3(CNMeXCNBu )2 from Mo(CO)6 in <25 min in 85 and 95% yields, respectively (159). 

Replacement of ligands in C3H5MoCl(CO)2(NCMe)2 by isocyanides has given the substituted products C3H5MoC1(CO)2(CNR)2 (R = alkyl) and C3H5MoC1(CO)(CNBu )3, and the reduced products [MoC1(CNBu )4]2 and m-Mo(CO)2(CNR)4 (R = Me, Et). No rationale for the loss of allyl and allyl chloride in the latter two cases was proposed (206). These reactions are rare examples of the formation of low-oxidation state metal-isocyanide complexes via reductive elimination of allyl or allyl chloride from metal-allyl species. The potential applications of mono-, bis-, and tris-n-allylic systems as precursors to low-oxidation state compounds remain to be explored. Substitution and simultaneous reduction of Mo(SBu )4 also occurred on reaction with CNBu to give Mo(SBu )2(CNBu )4 (207) (see Section IV,D,2). 

For alcohol additions, mono- and dicarbene complexes have been synthesized, for palladium, platinum (487-489), and gold (475, 490- 493), from methanol, ethanol, or ethanethiol (494) additions to the isocyanide precursor. The stability of the gold(I) carbenes can be gauged from reactions with halogens which gave the oxidative addition product without loss of the carbene ligand (492). 

The UDC concept can be further extended by application of ethyl glyoxylate (a convertible aldehyde ). Simple reaction of 48 in the Ugi MCR with /V-Boc anthranilic acids, /V-Boc-rt-amino acids, mono-A-Boc diamines, and niono-A-Boc phenylenediamines, followed by acid treatment and in some cases proton scavenging, affords 1,4-benzodiazepines 49, diketopiperazines 50, ketopiperazines 51, and dihydroquinoxalinones 52, respectively.25 Note that products differ from those obtained from convertible isocyanides in that they contain an additional exocyclic amide... 

Hatanaka and co-workers found that carbapenem derivatives were readily available by means of an Ugi-4CR between 3-aminoglutaric acid mono-t-butyl ester, formaldehyde, and 4-nitrobenzyl isocyanide that gave the /l-lactam 156, which was converted into the 4-nitrobenzyl ester 157. The subsequent stereoselective Dieckmann condensation allowed the preparation of the 2-oxocarbapenem derivative 158 (Scheme 2.57) [87]. 

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