No abstract

Structurally different ketones can be alkylated at the a-position via their silyl enol ethers with terfalkyl halides in the presence of Lewis acids such as titanium tetrachloride (-27-35). Concerning the alkylation agent, the position specific introduction of branched and cyclic krf-alkyl groups is possible ( 4 4 1 -49). Bridgehead halides of the type 1-adamantyl bromide react analogously ( 4 2 -61). Silyl enol ethers derived from unsymmetrical ketones react regiospecifically (+63, 64, 66, 67). If the reaction partners contain additional functional groups such as aryl residues (-68, 69) or ester groups (-71) or primary alkyl halide moieties (-+73), selectivity in the desired manner is observed. a,a'-Bis-terf-alkylated ketones (74 -76) are also easily accessible, but not the a , a-isomers.

No abstract

The antiviral activity of some α‐adamantyl carbonyl compounds of type (3) is greater than that of 1‐amino‐adamantane. Syntheses of the kind shown below are therefore of considerable interest.

Mono‐ and bicyclic as well as spirocyclic carbonyl compounds can be prepared by intramolecular tert‐alkylation of olefins such as (1) with SnCl4. An O‐stannyl derivative and a carbenium ion are probably intermediates in the reaction, which should find application in terpene and steroid syntheses.