Carbocyclic acids

Lactams Lactams represent a special type of C=N system due to the tautomerization between the lactam (keto amine) and lactim (hydroxyimine) forms. The lactim form is much more favored for cyclic than for non-cyclic amides of carbocyclic acids. In the reaction of complex 2b with N-methyl-e-caprolactam, a simple ligand exchange reaction occurs and complex 87 can be isolated. With P-propiolactam, the alkenyl-amido complex 88 is formed, which indicates an agostic interaction. The reaction of complex 1 with e-caprolactam gives, after elimination of the alkyne and of molecular hydrogen, complex 89 with a deproto-nated lactam in a r]2-amidate bonding fashion [47]. 

Several multi-component domino reactions for the preparation of libraries have been developed in the last years.141 One of the first examples in solution is a four-component reaction described by Ugi et al. in which a carbocyclic acid 5, an aldehyde 6 and an isocyanide 7 are condensed in presence of methanol to give amino acids 8 (scheme 2).151... 

Tokuyama H, Yamago S, Nakamura E, et al. (1993) Photoinduced biochemical activity of fullerene carbocyclic acid. J Am Chem Soc. 115 7918-7919. 

Unsaturated carboxylic acids can be de-carboxylated to alkyl radicals that undergo an intramolecular addition. The S-exo-trig-cyclization of fi-allyloxy radicals, generated from an appropriate carboxylic acid, combined with a final heterocoupling has been applied to synthesize a precursor of prostaglandine PGF2q (Fig. 47) [246] and a branched carbohydrate (ratio of diastereo-mers 1.8 1) (Fig. 48) [247]. A radical tandem cyclization of a doubly unsaturated monocyclic carbocyclic acid provides a... 

Another type of elimination reaction favoured under plasma conditions is the decarboxylation. Carbocyclic acids easily lose carbon dioxide to form the parent hydrocarbons. In acid anhydrides decarboxylation is followed by a decar-bonylation. Cyclic or bicyclic anhydrides fragment forming unsaturated compounds, a reaction which has been studied with phthalie anhydride 24>. This anhydride decomposes to dehydrobenzene which, in the absence of other compounds, dimerizes, trimerizes or polymerizes. Orientation experiments indicated similar results for aliphatic acid anhydrides. 

An asymmetric procedure was reported by Trost in 1989 [16]. The combination of [Pd2(dba)3]CHCl3, a chiral carbocyclic acid such as Mosher s acid, and (S)-binaphthoic acid resulted in low but promising induction (33 % ee). Enantioselec-... 

The Passerini reaction is a useful method for the synthesis of substituted a-acyloxy carbocyclic acids. This is another reaction that one might assume an epoxide would not survive. Reaction of an epoxy aldehyde with benzoic and TosMIC provided the Passerini product in good yield as a mixture of diastereomers <07SL83>. 

In some cases it is appropriate to use an imine instead of a carbonyl compound. Thus, benz-alaniline reacts with activated methylenes in the presence of carbocyclic acid anhydrides to give the corresponding Knoevenagel products (Scheme 21) Similarly, the enamine (170) reacts with cyanoacetic acid in ethyl acetate or dimethylformamide to afford the cyclohexylidene compound (171 Scheme 28). Acetals may be employed instead of the free ketones. An example is the reaction of fluorenone cyclic acetal (172) with malon initrile, which occurs in butanol without added catalyst to af-... 

Esters of various carbocyclic acids are readily hydrosilylated to give products that are used as silane coupling agents according Eq. 2. [1, 2]. 

This method has been applied independently to the synthesis of steroid intermediates. A route to the carbocyclic acids (36), involving a Claisen rearrangement of silyl enolates obtained from the lactones (35), has been reported by which yields of between 70 and 96% were obtained for eight examples (Scheme... 

Enantiomerically pure a-acyloxy ketones were readily prepared by reacting alkyl, alkenyl, alkynyl and arylmanganese halides with chiral a-acyloxy carbocyclic acid chlorides (Scheme 13.22) [25]. The reaction takes place under mild conditions in ether or in TH F to give the expected ketones in high yields with an excellent enantiomeric purity. 

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