Fert-Butyl isocyanide

It is well known that isotactic polyolefins often exist as equimolar mixtures of right- and left-handed helices in the crystalline state [19,35]. Upon dissolution they typically undergo rapid conformational changes due to a lack of rotational barriers [36]. In 1974, Drenth demonstrated that polymers bearing bulky side groups exist as stable helices in solution by resolving poly(fert-butyl isocyanide) into optically active fractions [37]. 

OjMoNCioH, Molybdenum, (fert-butyl isocyanide)pentacarbonyl-, 28 143 OjNWCigH, Tungsten, (rert-butyl iso-cyanide)pentacarbonyl-, 28 143 0,N2 VC H , Tungsten, tetracarbonyl((di-ethylamino)methylidyne](isocyanato)-, trans-, 26 42... 

Yields higher than about 70% for any of these isonitrile preparations generally indicate incomplete fractionation. The purity of the product may be conveniently checked by proton magnetic resonance spectroscopy. The characteristic 1 1 1 triplet for fert-butyl isocyanide appears at 1.46 (chloroform-d). A small upheld peak usually indicates the presence of unreacted amine. Other common contaminants are dichloromethane and chloroform. The purity may be determined more accurately by gas chromatographic analysis on a 230 cm. by 0.6 cm. column packed with 10%SE30 on Chromosorb G, 60-80 mesh, at 80°. 

The use of phosgene in the presence of triethylamine has become an often applied method since Ugi s extensive works in this field [1157]. As a prelude to preparative isonitrile chemistry, Ugi s 1971 procedure for the production of tert-butyl isocyanide is presented [1165]. tert-Butyl formamide is dehydrated with phosgene to afford fert-butyl isocyanide in 82% yield. 

Typical procedure. N-tert-Butyi-N -n-butylcarbodiimide 1747 [1282] A mixture of fert-butyl isocyanide 1745 (2 mmol), n-butylamine 1746 (2 mmol), selenium (2 mmol), and DBU (8 mmol) was stirred for 1 h in refluxing THF (5 mL). Then, molecular oxygen was introduced by means of a peristaltic pump at 20 mL min for 5 h while maintaining reflux. After deposited selenium had been filtered off, the filtrate was diluted with Et20 (50 mL), washed with brine (3 x 50 mL), dried over MgS04, and concentrated in vacuo to give essentially pure 1747 in 82% yield. 

NiN4C2oH s, Nickel(0), tetrakis(fert-butyl isocyankle)-, 28 99 NiN C24H,s, Niekel(0), bis(UO-phenanthrolineK 28 103 NiN4C2,H44, Nkkd(0), tetrakis(cyck>hexyl isocyanide)-, 28 101... 

Cyclohexen-l-yl isocyanide 1521, rac-4-fert-butyl-cyclohexen-l-yl isocyanide, and rac-4-phenyl-cyclohexen-l-yl isocyanide were likewise prepared by a similar method using gaseous phosgene to furnish the vinyl isocyanides in yields of 71-80% [1168], These were applied in a multicomponent approach to novel totally protected precursors of PNA monomers through an Ugi 4CR. 

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