The synthesis of 5, 5-dimethylbicyclo [2.1.1] hexane-1-carboxaldehyde

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Ebisu, Kikuye
Organic compounds -- Synthesis
thesis / dissertation description
The highly strained bicyclo[2.1.1]hexane system has been of considerable interest to chemists especially in connection with bond angle deformation studies. Previous synthetic routes to the bicyclo[2.1.1]hexane system have largely involved photolytic ring contraction of the bicyclo[2.2.1]heptane system. The nitrous acid deamination of a bridgehead amino alcohol, 1-amino-3,3-dimethylbicyclo[2.2.1]heptan-2-ol(I), was studied with the hope that ring contraction would occur. The product of the reaction was an aldehyde which was readily oxidized by air. N.m.r. data indicated that the product was 5,5-dimethylbicyclo[2.1.1]hexane-1-carboxaldehyde (II), m.p. 84.5-88°; [α]D^23 -6.8°(benzene); 11 semicarbazone, m.p. 192-193.2° dec. The yield of aldehyde based on the semicarbazone was 76%. The aldehyde was oxidized with hydrogen peroxide to 5,5-dimethylbicyclo-[2.1.1]hexane-1-carboxylic acid, m.p. 120.2-122.2° ; [α]D^23 +11.2° (benzene). Synthesis of the bridgehead amino alcohol I involved rearrangement of 2-bromo-2-nitrobornane with silver nitrate to l-nitrocamphene (III). Evidence is presented in support of structure III. Ozonization of 1-nitrocamphene and reduction of the resulting nitro ketone yielded the bridgehead amino alcohol I, m.p. 100-102° ; [α]D^23 -10.3° (ethanol). Attempts to prepare another bridgehead amino alcohol, 1-amino-4-bromo-5,5-dimethylbicyclo[2.2.l]heptan-2-ol, were unsuccessful. Treatment of 4D bromo-5,5-dimethyl-2-hydroxybicyclo[ 2.2.1]heptane-1-carboxamide with sodium hypobromite in excess base yielded the 2-oxazolidone IV which decomposed at 212-222° The 2-oxazolidone was converted with sulfuric acid to a neutral ketone, m.p. 169.4-170.4°. Structure V is proposed for the compound on the basis of elemental analyses and spectral data.