R-Butyl isocyanide

The direct combination of selenium and acetylene provides the most convenient source of selenophene (76JHC1319). Lesser amounts of many other compounds are formed concurrently and include 2- and 3-alkylselenophenes, benzo[6]selenophene and isomeric selenoloselenophenes (76CS(10)159). The commercial availability of thiophene makes comparable reactions of little interest for the obtention of the parent heterocycle in the laboratory. However, the reaction of substituted acetylenes with morpholinyl disulfide is of some synthetic value. The process, which appears to entail the initial formation of thionitroxyl radicals, converts phenylacetylene into a 3 1 mixture of 2,4- and 2,5-diphenylthiophene, methyl propiolate into dimethyl thiophene-2,5-dicarboxylate, and ethyl phenylpropiolate into diethyl 3,4-diphenylthiophene-2,5-dicarboxylate (Scheme 83a) (77TL3413). Dimethyl thiophene-2,4-dicarboxylate is obtained from methyl propiolate by treatment with dimethyl sulfoxide and thionyl chloride (Scheme 83b) (66CB1558). The rhodium carbonyl catalyzed carbonylation of alkynes in alcohols provides 5-alkoxy-2(5//)-furanones (Scheme 83c) (81CL993). The inclusion of ethylene provides 5-ethyl-2(5//)-furanones instead (82NKK242). The nickel acetate catalyzed addition of r-butyl isocyanide to alkynes provides access to 2-aminopyrroles (Scheme 83d) (70S593). 

Below 100 °C tri-f-butyldiaziridinimine (176) only undergoes inversion at the exocyclic nitrogen, as evidenced by coalescence of NMR signals at about 50 °C. Heating for 1 h to 150 °C, however, results in clean formation of (E)-azoisobutane and r-butyl isocyanide. 

Macrolides.2 On treatment of 1 with r-butyl isocyanide, either 2a or 2b is formed, which on treatment with a carboxylic acid forms a mixture of the interconvertible 3a and 3b. When the R group of 3 bears a terminal hydroxyl group, lactonization occurs (with release of 1) very readily, even without silver ion catalysis (6,246). Work-up is particularly simple if the phenyl group is substituted by an amino group, which permits recovery of the thione reagent by a wash with dilute acid. 

Tetrakis(r-butyl isocyanide)dichlorodipalladium(I) is one of a very limited number of examples of the Pd(I) oxidation state. The convenient synthesis of this stable and easily soluble complex reported here should make it a useful starting material for continued study of the Pd(I) oxidation state. The synthesis may be successfully scaled down at least fivefold. 

The acid-catalyzed reaction of oxetanes with r-butyl isocyanide gives 2-iminotetra-hydrofurans, boron trifluoride etherate being used as catalyst (equation 26). The authors proposed that the isocyanide reacts with the protonated oxetanes by an S 2 mechanism (70S475). 

Cyanation of acetals was achieved either by means of r-butyl isocyanide or P-trimethylsilylethyl isocyanide in the presence of titanium(IV) chloride (equation 13) or by TMS-CN in the presence of electrogenerated acid. ... 

The 4CC of benzoic acid (58), isobutyraldehyde (59) and (S)-a-phenylethylamine (60), or their imine (61), with r-butyl isocyanide (26) has been studied quite extensively as a model reaction for stereoselective 4CC. " ... 

Substituted 1,2-naphthoquinones are formed by an intramolecular reaction of o-alkeny-latylcarbene complexes. With an electron-rich aromatic nucleus, the photoinduced benzannu-lation is sluggish. The use of r-butyl isocyanide instead of CO circumvents such problems. ... 

HN(f-Bu)COC6H2Me3. r-Butyl isocyanide also inserts into the chromium-carbon bond of the mesityl complex, but only a single insertion is observed, and Cr(=N-f-Bu)2 -[t-BuN=C(C6H2Me3)] (C6H2Me3) is formed. An ) -aminoacyl is also the product of the reaction between Cr(=N-f-Bu)2Cl2 it-BuNC) and methyllithium. Presumably, methyl replaces one of the chlorides, then migrates to the isocyanide carbon to give Cr(=N-f-Bu)2 [ 2-[f-BuN=C(Me)] Cl]. 

The parent TMM complex (190 R = H) undergoes photochemical ligand substitution with trifluorophosphine or trimethylamine M-oxide assisted substitution with tertiary phosphines or r-butyl isocyanide (Scheme 54). Trimethylamine -oxide assisted substitution using isoprene as the incoming ligand results in C-C bond formation to afford the bis-TT-allyl complex (197). An intramolecular version of this reaction is also known. The parent complex (190 R = H) reacts with electrophiles. Addition of HCl or Br2 gives the methallyl complexes (192) and (198), respectively. Tetrafluoroethylene adds across the Fe-C bond to afford (199) under photochemical conditions. Complex (190) undergoes Friedel-Crafts-type acylation with... 

Reaction of the Schiff base ligand Af,iV -bis(o-diphenylphosphinobenzylidene)(ethylene-diamine (49 en=P2) with AgBp4 produced a pale yellow salt. The IR spectrum of this complex showed strong bands due to the imino and BF4 group (v(0=N) 1653 cm , v(BF4) 1080 cm ). The crystal structure of the Cu analogue was reported and the copper ion was found to adopt a severely distorted tetrahedral geometry. This strain was manifested in its reactivity since both the copper and silver complex reacted with r-butyl isocyanide. In the case of silver(I) a five-coordinate adduct was obtained, [Ag(en=P2)(Bu NC)]BF4. ... 

Tsuda etalP also found that copper(i) f-butoxide in the presence of r-butyl isocyanide or certain other ligands (PEts, PPhs) reacted reversibly with carbon dioxide to give the f-butyl carbonate complex (Eq. 2.289) ... 

Reaction of TBO with (CH3CH20)2P(0)H in the presence of r-butyl isocyanide/ Cyclopropane... 

Isocyanide Polymers Bulky isocyanides give polymers having a 4 1 helical conformation (115) [154]. An optically active polyisocyanide was first obtained by chromatographic resolution of poly(r-butyl isocyanide) (poly-116) using optically active poly((S)-sec-butyl isocyanide) as a stationary phase and the polymer showing positive rotation was found to possess an M-helical conformation on the basis of CD spectral analysis [155,156]. Polymerization of bulky isocyanides with chiral catalysts also leads to optically active polymers. 

---