| Treatment of 3-methyl-2-buten-2-ol with and acetonitrile solution of excess lithium nitrate and trifluoroacetic anhydride layered with carbonate affords the rearranged nitrate ester, 3-methyl-3-buten-1-ol 1-nitrate, in 67% yield. This is the first example of formal [3,3]-sigmatropic rearrangement of an allyl nitrate ester. A second, more complex allyl alcohol, 3-methyl-1,6-heptadien-3-ol, was nitrated under similar conditions to give the rearranged nitrate ester, 3-methyl-2,6-heptadiene-1-nitrate, in 86% yield as a 66:34 mixture of E and Z isomers respectively. Purification via flash chromatography on silica gel gave low (13%) mass recovery. Two dimensional TLC analysis confirmed the decomposition of the nitrate ester on silica gel. The nitrate ester was converted by zinc reduction to 3-methyl-2,6-heptadien-1-ol in 45% yield as a 66:34 mixture of E and Z isomers respectively. Flash chromatography of 3-methyl-2,6-heptadien-1-ol provided a small amount (5% mass recovery) of the pure Z isomer, prior to coelution of the mixture. A controlled Sharpless epoxidation of the dienol E, Z-mixture with (+)-diisopropyl tartrate gave 3-methyl-2,3-oxiran-6-hepten-1-ol in 71% yield and the unreacted Z isomer (56% mass recovery). Nitration of 3-methyl-2-buten-1-ol afforded 3-(acetylamino)-3-methyl-2-nitrobutyl nitrate in 75% yield. Nitration of 2-methyl-2-butene with an acetonitrile solution of lithium nitrate and trifluoroacetic anhydride layered with sodium carbonate afforded N-(2-methyl-3-nitro-2-butyl)acetamide in 72% yield. Similar nitration of 1,1-diphenylethylene afforded &agr;-phenyl-beta-nitrostyrene in 52% yield. Nitration of 2,3-dimethyl-2-butene at 0-5 C afforded only N-(2,3-dimethyl-3-nitro-2-butyl)acetamide in 74% yield, while nitration at room temperature afforded two additional products, 3-(acetylamino)-2,3-dimethyl-2-butyltrifluoroacetate and N-(2,3-dimethyl-4-nitrobut-3-en-2-yl)-acetamide. Nitration of 1-methylcyclohexene with excess reagents led to the formation N-[(1r,2R,6S)-1-methyl-2,6-dinitrocyclohexyl]acetamide in 31% yield. Nitration of 1-methylcyclohexne with an acetonitrile solution of 1.1 equivalents of lithium nitrate and trifluoroacetic anhydride layered with sodium carbonate afforded NA¬-[(R*,R*)-1-methyl-2-nitrocyclohexyl]acetamide, N-[(R*,S*)-1-methyl-2-nitrocyclohexyl]acetamide, and 2-methyl-3-nitro-1-cyclohexene. Nitration of 4-methyl-3-penten-2-one gave N-(2-methyl-3-nitro-4-oxo-2-pentyl)acetamide in 43% yield under one set of conditions and N-(2-methyl-1-nitro-2-propyl)acetamide in 60% yield under slightly modifiedf conditions. Nitration of 3-methyl-1,3-pentadiene gave N-(3-methyl-4-nitro-1-pent-2-enyl)-N-nitroacetamide in 60% yield. 3-(Acetylamino)-2,3-dimethyl-2-butyltrifluoroacetate underwent cyclization to form 2,4,4,5,5-pentamethyl-2-oxazolinyl trifluoroacetate which gave 2,4,4,5,5-pentamethyl-2-oxazoline on treatment with base. Michael additions were performed on N-(2-methyl-3-nitro-2-butyl)acetamide using methyl acrylate and acrylonitrile. Methyl 5-acetylamido-4-nitro-4,5-dimethylhexanoate and N-(5-cyano-2,3-dimethyl-3-nitro-2-pentyl)acetamide were obtained in 51% and 48% yield respectively. Michael addition of NA¬-1-methyl-2-nitrocyclohexyl]acetamide and methyl acrylate gave methyl 3-[2-(acetylamino)-2-methyl-1-nitrocyclohexyl]propanoate as a single diastereomer in 61% yield. This is attributed to favorable internal H-bonding between the acetamide NH proton as the donor and a nitronate O-atom as the acceptor leading to selective isomer formation. Modified Nef reactions were performed on N-(2-methyl-3-nitro-2-butyl)acetamide and N-(2-methyl-1-nitro-2-propyl)acetamide to give N-(2-methyl-3-oxo-2-butyl)acetamide in 63% yield and 2-(acetylamino)-2-methylpropanoic acid in 85% yield. N-(2-Methyl-3-nitro-2-butyl)acetamide and N-[(1r,2R,6S)-1-methyl-2,6-dinitrocyclohexyl]acetamide were reduced with nickel (II) chloride and sodium borohydride to afford 3-(acetylamino)-3-methyl-2-butylammonium chloride in 52% yield and N-[(1r,2R,6S)-2,6-diamino-1-methylcyclohexyl]acetamide in 71% yield respectively. Debromination of 2,4-dibromo-2,4-dinitropentane with excess sodium iodide and acetic acid afforded 2-bromo-2,4-dintropentane in 77% yield. The second Br-atom could not be removed by these reagents. |
PDF Full Text Request