Isocyano-, ethyl ester

Methyl formate Formic acid, methyl ester (8,9) (107-31-3) Ethyl isocyanoacetate Acetic acid, isocyano-, ethyl ester (8,9) (2999-46-4)... 

It is assumed that both reactions start with the formation of the imine of the acyclic structure of carbohydrates with proline. After this initial step, the cyanoacetate 86 dictates aKnoevenagel/Michael cascade, whereas by employment of isocyanoacetate 87 a nucleophilic addition of the carbon atom of the isocyano group and subsequent rearrangement reaction are observed. An explanation for this different behavior of the isostructural compounds (ethyl esters 86 and 87) depicted in Scheme 2.18 is given by the different sites of highest nucleophilicity as described by Mayr et al. [41]. These mechanistic considerations are depicted in Scheme 2.19. 

Bis(bromomethyl)quinoxaline (296) gave either 6,8-dihydrofuro[3,4-g]qui-noxaline (297) (NaOH, H20-MeCN, BU4NHSO4, no further details 84%) or ethyl 7-isocyano-7,8-dihydro-6//-cyclopenta[g]quinoxaline-7-carboxylate (298) (Et02CCH2NC, K2CO3, BU4NHSO4, MeCN, no further details 38%) and thence the 7-amino ester (HCl-EtOH, no further details 90%). ... 

Arylsulfonyl methyl isocyanides (3) and isocyano esters (1) can also be prepared by the deprotonation of alkylisocyanides (5) by strong bases (nBuLi or NaH) followed by the addition of TosF and dialkyl carbonates or ethyl chloroformate, respectively (pathB) [37, 38]. However, the use of small and foul-smelling alkyl isocyanides makes this route less attractive. 

Typical procedure. tert-Butyl 2-isocyano-4-methyl pentanoate 1554 [1182] N-Formyl-leucine tert-butyl ester 1553 (5.00 g, 23.2 mmol) and triethylamine (7.13 g, 69.7 mmol) were dissolved in dichloromethane (36 mL) and the solution was cooled to 0 °C. At this temperature, a solution of triphosgene (2.30 g, 7.74 mmol) in dichloromethane (25 mL) was added dropwise. The mixture was stirred for 2 h at room temperature, water (5 mL) was then poured into it, and the phases were separated. The organic layer was washed with 5% aq. sodium hydrogen carbonate solution, dried over sodium sulfate, and concentrated in vacuo. The residue was chromatographed on silica gel eluting with ethyl acetate to furnish tert-butyl 2-isocyano-4-methyl pentanoate 1554 (4.29 g, 94%) as a colorless oil. 

Typical procedure. 4-Bromo-3-[2-isocyano-2-(methoxycarbonyl)ethyl]ir dole-l-carboxylic acid tert-butyl ester 1559 [1187] The N-formyl-N -Boc-4 -bromo-tryptophan methyl ester 1558 (0.05 g, 0.14 mmol) was suspended in dry dichloromethane (3 mL) under argon and the solution was cooled to below 0 °C using an ice/salt bath. Tri-ethylamine (0.09 g, 0.86 mmol) was added through a septum, and then a solution of triphosgene (0.014 g, 0.05 mmol) in dichloromethane (1 mL) was added dropwise. The solution was allowed to warm to room temperature and stirred for a further... 

Protected aldono-1,4- or -1,5-lactones [e.g. (316)] reacted with ethyl isocyano-acetate and base in an aprotic medium to give either a-(formylamino)acrylic ester derivatives [e.g. (317)] or, where base-catalysed elimination reactions can be suppressed, acyclic oxazole derivatives [e.g. (318)]. ... 

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