Urethans methylamines

This is a powerful explosive, stronger than tetryl but weaker than cyclonite. It is, however, of no practical value chiefly because its preparation is too expensive, requiring first the conversion of methylamine into urethane and then into its nitro derivative. On hydrolysis the latter yields methylnitramine. Similarly, the hydrolysis of dinitrodimethyloxamide (p. 35) leads to the formation of methylnitramine. 

The original method of preparing diazomethane is as follows. Methyl-urethane, formed by the interaction of methylamine and chloroformic ester, is converted into the nitroso compound by the action of nitrous acid, the latter yielding diazomethane on treatment with alcoholic potash. 

New total syntheses9 of azabicyclo[4.2.1]nonanone (10) have now been elaborated. The first synthesis started with 5-azidocyclo-oct-l-ene (7). Reduction and iV-methylation (via the urethane), followed by treatment of the secondary amine with hypobromous acid and with base, gave a mixture of 9-methyl-9-azabicyclo[4.2.1]nonan-2a-ol (8) and its 2/3-isomer (9), contaminated with some azabicyclo[3.3.1]nonane analogue cf. (18). The second synthesis starts with the monoepoxide from cyclo-octa-1,5-diene (11). Treatment with methylamine and... 

The best known and most widely used diazoalkane is diazomethane (95 equation 39). Preparative methods for diazomethane involve, in general, the nitrosation of a methylamine derivative (93), followed by cleavage under alkaline conditions. Methylamine derivatives used have included the urethanes, ureas,carboxamides, sulfonamides, guanidines and even the methylamine adducts of unsaturated ketones and sulfones. N-nitroso-N-methyl p-toluenesulfonamide (Diazald, Aldrich) is currently the most commonly used diazomethane precursor. Diazomethane is both toxic and explosive. Although in the past it has been purified by codistillation with ether, it is now usually generated, stored and used as an ether solution without distillation. 

Diimide reduction of 96, obtained by the enzymatic oxidation of 95 (96% ee) [67], followed by O-acetylation afforded cyclohexene-diol 97 in 47% yield (Scheme 19). Compound 97 was converted into carbamate 98 by S 2 reaction with methylamine and subsequent urethane formation. Regioselective protection of the diol in 98 with TBSC1 afforded 99, which was coupled with bromoisovanillin 54 under the conditions of Mitsunobu to provide 100 (see Sect. 2.2.2). The intramolecular Heck reaction of 100 constructed the benzofuran ring including a quaternary center to afford 101 in 82% yield. Wittig reaction of 101 with Ph3P=CHBr generated vinyl bromide 102 in 49% yield as a mixture of E- and Z-isomers (E Z = ca. 1 2). 

Polycarbonate Makrolon pieces 1 (5 g) were placed in a short column with glass frit and ground joints fitted to a flask with evaporation facility and with a gas supply at the top. After evacuation and closing with a stopcock a constant pressure of 0.9-1 bar of methylamine gas was applied and maintained for 1-3 h, depending on the size of the pieces of 1, until all of it had liquefied and dropped into the flask. The residual gas was recovered from a trap at 77 K. The liquid contained (V.A -dimcthylurca 2 and bisphenol A 3a as the major products and also some urethane and bisurethane 3 b, ready for separation work-up. 

Fluorescence detection is not nearly as widely used as UV detection since most carbamates possess no native fluorescence. However, the structure of these pesticides contains a V-methyl substituted urethane with variations in the ester moiety. The common methylamine functionality allows the detection of compounds via a two-stage postcolumn reaction. Carbamates in the column effluent are first hydrolyzed with NaOH at a high temperature to form methylamine, which is converted into a fluorophore compound by addition of 6>-phthaldehyde (OPA) and... 

Reductive cleavage of urethanes. The last step in a synthesis of 2,7-epH )-perhydrohistrionicotoxin (2) involves cleavage of the urethane group of (1) with excess lithium in methylamine at -78°. ... 

Methylamine Methylamine, aqueous solutions Octylphenol Propyl mercaptan 1,2,4,5-Tetrachlorobenzene Urethane... 

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