Isonitrile epoxides

Unusual triethylamine-catalysed rearrangements of bicyclic endoperoxides derived from substituted cycloheptatrienes have produced383 a variety of products (see, e.g., Scheme 80). Ab initio calculations have shown that energised 2,3-epoxypropoxide anions undergo a degenerate Payne rearrangement in the gas phase via a three-centre mechanism.384 It has been reported385 that treatment of isonitrile epoxides (330) with... 

A very common combination in Pd-catalyzed domino reactions is the insertion of CO as the last step (this was discussed previously). However, there is also the possibility that CO is inserted as the first step after oxidative addition. This process, as well as the amidocarbonylation, the animation, the arylation of ketones, the isomerization of epoxides, and the reaction with isonitriles will be discussed in this section. 

C=0)-halogen, 0-(C=0)-halogen, S02-halogen, N=C=0, N=C=S, N-C(=S)-N Acyclic C(=0)-S, acyclic C(=S)-0, acyclic N=C=N Anhydride, aziridine, epoxide, ortho ester, nitroso Quaternary amines, methylene, isonitrile Acetals, thioacetal, N-C-O acetals Nitro group, >1 chlorine atom... 

Under acidic reaction conditions the formation of isonitriles can compete efficiently with nitrile formation (Scheme 4.87) [377]. Particularly effective reagents for the formation of isonitriles are mixtures of Me3SiCN with Lewis acids such as Zn(II), Pd(II), or Sn(II) salts. Aluminum-derived Lewis acids with Me3SiCN, on the other hand, mediate the conversion of epoxides into nitriles [378, 379]. 

Beside classical Zr P bond cleavage with the release of the corresponding phosphane, ketones, aldehydes, nitriles, isonitriles, and epoxides have been inserted into the Zr-P bonds of fom- or five-membered phosphazirconacycles leading to ring expansion. For example, the equation (7) shows the insertion of acetonitrile in a triphosphanato complex affording an unsymmetrical six-membered ring complex. ... 

In studies directed towaids the synthesis of the fungal isonitrile antibiotic isonitrin B (103), a cy-clopentanoid metabolite related to trichoviridine (104), various trialkylsilyl enol ethers were irradiated with propionaldehyde to produce equimolar amounts of stereoisomeric bicyclic oxetanes (105). The corresponding silyl dienol ethers, however, gave little oxetane product owing to preferential diene photopolymerization. The use of vinyl epoxide derivatives such as (106), however, offers a possible access to the epoxycyclopentanoid system with simultaneous control of the face selectivity of the photoaddition by the epoxide moiety. 

Conjugated isonitriles. Isocyanoalkyl epoxides undergo ring opening by reaction with LHMDS. The ( /Z)-isomer ratios are different from (usually higher than) those arising from using LDA. 

The Lewis acid-catalyzed reaction of epoxides with TMSCN leads to the formation of -siloxy-nitriles or -isonitriles [604]. The reaction pathway depends mainly on the Lewis acid used. The Yb(CN)3-catalyzed reaction of epoxides proceeds stereospecifically to give y3-siloxynitriles in good yields (Scheme 10.238) [624a]. 

Chlorination of phosphines. Both trialkyl- and triarylphosphines afford the dichlorides on reaction with triphosgene, which can then be used to convert epoxides to 1,2-dichloroalkanes, aldehydes to gem-dichlorides, amides to nitriles, formamides to isonitriles, ureas to carbodiimides, and amines to triphenylphosphoranylimines. 

The procedures in Sect. 4 give some representative examples of metallation of nitriles and isonitriles and reactions of the anionic intermediates with alkylating agents, epoxides, aldehydes, and ketones. Syntheses involving the generation of anionic intermediates (mostly in small concentrations) and their immediate further reaction with an electrophile present in the medium during this generation fall beyond the scope of this book. 

Addition of the carboxylic acid and the isonitrile. Dissolve the m selected carboxylic adds in 0.25 ml. of methanol/mL of slurry. Each carboxylic add is in 5 molar excess to the amount of epoxide in the gel. Finally, add a fixed aliquot (0.25 mL) of the isopropyl isocyanide (II, Table 2) component (5 molar excess, in methanol) into each of the (wx m) wells (see Note 10). Incubate the reactants at 50°C in a rotary shaker (200 rpm) for 48 h. At the end of the synthesis, wash the gels with appropriate solvents. Weigh the gels, and store at 0-4°C in 20% (v/v) ethanol (see Notes 11 and 12). 

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