Unsaturated Alicyclics

Carbocyclic compounds are very usefully divided into (a) saturated (alicyclic) compounds, (b) aromatic compounds and (c) the intermediate partially unsaturated (alicyclic) compounds. Heterocyclic compounds can be subdivided in exactly the same way, and equally usefully. 

In the main, the physical and chemical properties of saturated and partially unsaturated alicyclic compounds closely resemble those of the analogous acyclic compounds formally derived by cleavage of the carbon ring at a point remote from any functionality. Relatively small, but often significant, differences in properties arise from conformational effects, and from strain effects in small rings, and these differences can be striking in properties which are particularly sensitive to molecular shape. 

Class 2.2 Unsaturated alicyclic rings attached aliphatic chains... 

Unavailable because experimental methods for estimation of this parameter for unsaturated alicyclic alcohols are lacking in the documented literature. However, its high solubility in water suggests its adsorption to soil will be nominal (Lyman et al., 1982). 

Table 4. Formation of Fluorinated Unsaturated Alicyclic Compounds by Dehalogenation...

It is not very likely that the influence of a double bond extends far over a chain of carbon atoms. For example, it is difficult to believe that a double bond at one end of the cetene-1 molecule containing 16 carbon atoms has an effect on hydrogen exchange at its other end. It is more likely that complete hydrogen exchange in alkene molecules and unsaturated alicyclic hydrocarbons is due to multiple bond migrations, i.e. isomerization of the hydrocarbon. 

It would be interesting to carry out analogous experiments with unsaturated alicyclic hydrocarbons whose side-chain is separated from the ring by a tertiary carbon atom. It would also be desirable to measure the kinetics of hydrogen exchange for non-equivalent atoms in alkene molecules, and to compare the rates of deuterium exchange and isomerization, and also the rates of all these processes in hydrocarbons of similar composition with double and triple bonds, and so on. 

The Cannizzaro reaction of heterocyclic aldehydes has been examined in a few cases only. Furfural,83 a-thiophenealdehyde,84 and a-pyridylal-dehyde 86 undergo the reaction normally to give the expected products. 3-Formyl-l,2,5,6-tetrahydro-l-ethylpyridine resinifies upon treatment with potassium hydroxide,86 a behavior consistent with the observation that it is structurally similar to an a,/3-unsaturated alicyclic aldehyde. 3,4-Dibromothiophene-2,5-dialdehyde undergoes a complex series of reactions, involving both cleavage (loss of —CHO) and dismutation, when treated with alkali.87 Of particular interest in this connection is the fact that under certain conditions the ester composed of the usual... 

The following tables are intended to include all the reductions with aluminum alkoxides which were reported prior to February, 1943, although some examples doubtless have been overlooked. Table I lists the reduction of aldehydes, which have been subdivided into (a) aliphatic aldehydes and (b) alicyclic and aromatic aldehydes. Table II lists the reduction of ketones, which have been classified as (a)-satu-rated and unsaturated aliphatic ketones, (b) aromatic ketones, (c) alicyclic ketones, (d) unsaturated alicyclic and aromatic ketones, (e) a- — halogen substituted ketones, (f) diketones, (g) protected diketones, (h) alcoholic and phenolic ketones (and ethers or esters of these), and (i) keto esters. 

A more direct method for the enantioselective ring opening of unactivated bicyclic /3-lactams has been reported. When lipolase (modified lipase B from Candida antarctica adsorbed on a macroporous resin) was allowed to interact with racemates 126 (n 1 or 2) and 127 (n= 1 or 2) in aqueous diisopropyl ether at 70 °C for 4.5-7 h, the products were the enantiomerically pure ring-opened unsaturated alicyclic /3-amino acids 128 (n = 1 or 2) and 129 (n 1 or 2), and the bicyclic /3-lactams 130 ( = 1 or 2) and 131 (n = 1 or 2) in 45 48% yield with ee 95-99% (Equations 13 and 14) <2004TA2875>. 

The dihydro-1,3-oxazine route has been extensively investigated by Meyers. Controlled reduction to the tetrahydro derivative (53), followed by hydrolysis, gave good yields of the corresponding aldehyde or deuteriated aldehyde, R—CDO (Scheme 22). ° Further development of this concept has subsequently given rise to convenient routes to acyclic, a,3-unsaturated, ° alicyclic, y-hydroxy and y-oxo aldehydes. Full synthetic details of these and other variants of the Meyers aldehyde synthesis have been published. ... 

The reactivity of four oxidizing reagents, sodium bismuthate, sodium periodate, manganese dioxide and lead tetraacetate, has been compared in the oxidative cleavage of unsaturated alicyclic a-ketols to a)-oxo-a,j8-unsatu-rated acids [93JOC2196]. Sodium bismuthate cleaved saturated a-ketols but not unsaturated ones (Scheme 5.3). 

Ammonolysis of alicyclic anhydrides followed by Hofmann degradation is one of the most frequently used methods for the synthesis of alicyclic P-amino acids, since many anhydrides are commercially available cheap substances produced by Diels-Alder addition of maleic anhydride and the corresponding dienes [44], By this method, cis- and frans,-2-aminocyclohexane- and -cyclohexenecarboxylic acids, cis-2-aminocycloheptanecarboxylic acid [45], 3-ewtffo-aminobicyclo [2.2.1 ]heptane-2-ew/o-carboxylic acid, 3-e ifo-aminobicyclo[2.2.1 ]hept-5-ene-2-ertcarboxylic acid and some analogue P-amino acids have been prepared [44, 46-48], For partially unsaturated alicyclic compounds, a modified Hofmann degradation is used, sodium hypochlorite being applied to avoid bromine addition to the double bond [48,49]. 

Unsaturated alicyclic amides yield five-membered or six-membered bicyclic imides, depending on the position of the double bond. 

Isomerizations also occur during the carbonylation of unsaturated alicyclic amines for example, the carbonylation of (3-cyclohexenyl-methyl) amine leads, besides the expected bicyclic six-membered lactam, also to a five-membered lactam. 

Unsaturated alicyclic alcohols also give lactones. The reaction of (3-cyclohexenyl)methanol leads not to the expected bicyclic 8-lactone but to the isomeric bicyclic y-lactone, probably again by isomerization of an intermediate cobalt complex. 

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