Reaction with alicyclic compounds

Chapters V-X deal respectively with Heterocyclic and Alicyclic Compounds Miscellaneous Reactions Organic Reagents in Inorganic and Organic Chemistry Dyestuffs, Indicators and Related Compounds Some Physiologically-Active Compounds and Synthetic Polymers. Many of these preparations are of course intended for advanced students, but a mere perusal of the experimental details of selected preparations by those whose time for experimental work is limited may assist to impress them on the memory. Attention is particularly directed to the chapter... 

At higher temperatures the mixture of 10 and methyl vinyl ketone yields the 1,4-carbocyclic compound as described previously. Methyl isopropenyl ketone (5), ethyl acetylacrylate (d), 2-cyclohexenone (21), and 1-acetyl-1-cyclohexene (22) also undergo this type of cyclization reaction with enamines at higher temperatures. This cycloalkylation reaction occurs with enamines made of strongly basic amines such as pyrrolidine, but the less reactive morpholine enamine combines with methyl vinyl ketone to give only a simple alkylated product (7). Chlorovinyl ketones yield pyrans when allowed to react with the enamines of either alicyclic ketones or aldehydes (23). 

Non-Kolbe electrolysis of alicyclic p-hydroxy carboxylic acids offers interesting applications for the one-carbon ring extension of cyclic ketones (Eq. 35) [242c]. The starting compounds are easily available by Reformatsky reaction with cyclic ketones. Some examples are summarized in Table 13. Dimethylformamide as solvent and graphite as anode material appear to be optimal for this reaction. 

Only a few examples of ring syntheses by transformation of another ring have been published, as exemplified by the preparation of the sultines 168 by ring enlargement of five-membeted thiolane 1-oxides 166 (cf Section 8.10.9.2.3) and the 3,6-dihydro-l,2-dithiins 202 by catalytic transformation of vinylthiiranes 201 (cf Section 8.10.9.4.2). Because possibilities to synthesize six-membered rings with oxygen and/or sulfur as heteroatoms in 1,2-positions are rather limited, these reactions have been covered already in Section 8.10.9 together with alternative syntheses from alicyclic compounds. 

The reaction of phenols with alicyclic 1,3-dicarbonyl compounds in phosphorus oxychloride or sulfuric acid also leads to 3,4-fused coumarins (40JA2405). Dehydrogenation to the dibenzopyranone occurs on heating with sulfur or with palladium-charcoal (73CB62). 

Cycloaddition reactions represent a very versatile route to alicyclic compounds. The most important for six-membered rings is the Diels-Alder reaction, and its great utility lies in the fact that it is both regioselective and stereospecific. The reaction involves compounds containing a double or triple bond, usually activated by conjugation with additional multiply-bonded systems (carbonyl, cyano,... 

Reactions of the replacement by hydrogen of the tertiary nitro group in aliphatic and alicyclic compounds were recently described by Kornblum and co-workers (145). They occur at room temperature when the nitro compounds are treated with the sodium salt of methyl mercaptan. 

Tosylmethyl isocyanide (TsMIC) (120) is an easily prepared sulfone with a wide repertoire of useful reactions thus, TsMIC may be converted to ketones (121), alkanes (122) and alicyclic ketones (123) and (124), as shown in Scheme 52. The alicyclic compounds formed may be either small rings, e.g. cyclobutanone (123), or medium-sized rings like the 10-membered compound (124). In these reactions, the utility of TsMIC (120) is dependent on the good leaving group capacities of the tosyl and isonitrile moieties. The reagent (120) can also be used to synthesise heterocycles, e.g. oxazoles (125) (Scheme 53). 

In fact, reactivity of 1-chloro cycloheptene looks like reactivity of 1-chloro cyclohexene95,103,10S and reactions with nucleophilic complex base NaNH2-enolates lead to compounds similar to the ones isolated in cyclohexenic series. This is exemplified in Scheme 65 with alicyclic ketone enolates. 

There is now general agreement that Vilsmeier reactions with acetals, ketals, and the corresponding thio derivatives proceed by loss of a molecule of alcohol or thiol to give the reactive unsaturated ether or thioether with cyclic ketals the alcohol remains tethered, and may be chlorinated. The acetals and ketals are often more readily available than the unsaturated ethers, and yields of products are similar. A wide range of aliphatic and alicyclic acetals and ketals has been formylated the reaction can tolerate bulky groups at either end of the double bond, as is shown for compound 64 (Eq. 51). Products are isolated as iminium sails... 

Alumina is less widely used than silica due to its propensity to catalyse reactions with base-labile molecules and to cause rearrangements and even ring expansions in unsaturated and alicyclic compounds [11]. 

Cycloaddition of 1,3-dipolarophiles to alkynes for the synthesis of diazo compounds can also be applied to reaction of diazoalkanes with alkynes (2-91). 2-Diazopropane and 1,2-diarylethynes readily form 3//-pyrazoles (2.229). These pyrazoles isomerize photochemically to the 4-diazo-2-methyl-3,4-diarylbutenes (2.230), i.e., to a vinyldiazo compound (Pincock et al., 1973 Arnold et al., 1976 Leigh and Arnold, 1979). Some cyclopropene (2.231) is formed in a consecutive dediazoniation, i. e., by cyclization of the carbene formed. The method is not useful for unsymmetrically substituted alkynes because these cycloadditions are not regiospecific. It is, however, applicable to the synthesis of diazoalkenes with alicyclic... 

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