5-Methyl-2-hexanone, synthesis

The synthesis of the 1-methyl derivative of sempervirine was achieved by Woodward and McLamore who condensed 1-lithio-methyl-9-methyl-jS-carboline (386) with 2-isopropoxymethylenecyclo-hexanone (387) treatment of the reaction product with hydrochloric acid gave im -W-methylsempervirinium chloride (cf. 388). 

Probkm 28.28 Using 9-BBN plus any alkenes and unhalogenated acids or ketones, outline all steps in the synthesis of (a) 2-heptanone (b) 4-methylpentanoic acid (c) 4-methyl-2-hexanone (d) l-cyclohexyl-2-propanone (e) ethyl (trans Z-methylcyclopentyl)acetate (f) l>phenyl-4-methyM-pentanone (g) i-cyclopentyl-33 dimethyl-2-butaBone. 

Various other rhodium catalysts can initiate hydroacylation reactions. Thus, the indenyl complex [075-C9H7)Rh(J72-C2H4)2] is used in intermolecular hydroacylation44. Rhodium zeolites (RhNaX and RhNaY type zeolites) act as bifunctional catalysts for the synthesis of 2-methyl-3-hexanone and 4-heptanone (1 2 ratio) from propene, carbon monoxide and hydrogen53. In this case, the ketones may be formed via hydrocarbonylation (vide supra), however, according to control experiments, rhodium-free zeolites alone catalyze ketone formation from propene and butyraldehyde53. 

Two sets of ketone and alkyl halide could be used for the synthesis 3-hexanone and a methyl halide or 3-pentanone and an ethyl halide. 

Show a retrosynthesis and a real synthesis for preparing 2-methyl-3-hexanone from 1-propanol. 

An interesting and unusual synthesis of racemic leucine (Leu, L) was carried out as shown in Scheme 12.34 and reported early in the twentieth century. As shown, 2-methyl-l-propanol was converted to the corresponding iodide with hydrogen iodide (HI) and the primary alkyl iodide reacted with sodium salt derived from methyl acetoacetate to yield 5-methyl-3-carboxymethyl-2-hexanone. This, treated with nitrosyl sulfate (0=N-0S03H), yields the decarbonylated methyl 5-methyl-pentanoate-2-oxime. Reduction of the latter produced racemic leucine (Leu, L). 

A method for incorporation of a carbon-14 label in the ring geminal methyl groups of retinyl acetate has been described by Colwell et aL (1979). The synthesis, shown in Fig. 14, involves monomethylation of 2,6-dimethylcyclo-hexanone (LII) with methyl-iodide as catalyzed by potassium hydride. The trimethylcyclohexanone (LIU), labeled in one methyl group, was condensed with the 11-carbon acetylenic side chain (LIV) to give the acetylenic carbinol... 

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