Di , cyclic

Similarly pinane, the saturated di-cyclic terpene containing a telra-methylene group, is not a natural product but the corresponding unsaturated terpene with one double bond analogous to menthene is the chief constituent of turpentine. It is known as pinene and has the following constitution. 

The most important di-cyclic terpenes belong to the camphane group in which a penta-methylene ring is present. This five carbon... 

The most important of all of the oxygen derivatives of the terpene hydrocarbons are those of the di-cyclic group. Of these the most common is the well-known substance camphor, also termed Japan camphor. It is a ketone derivative of a di-cyclic terpene of the cam-phane type known as Bomylene. The corresponding alcohol derivative is known as Bomeol, or Borneo camphor. 

They are derivatives of saturated di-cyclic terpenes which in turn are related to the unsaturated di-cyclic terpenes thujene and fenchene which we have previously discussed (p.p. 822, 824). 

Camphor and Bomeol are therefore derived from a camphane di-cyclic terpene in which the isopropyl group joins the para carbons. The unsaturated di-cyclic terpene corresponding to camphor was at first supposed to be camphene but later work has proven that it is not camphene but Bornylene which has the structure corresponding to camphor. The constitution of camphene is still unestablished. 

Synthesis of Camphor.— The relationship of camphor to pinene, the terpene present in turpentine, is of especial interest and importance in connection with its synthesis. Pinene is the unsaturated di-cyclic terpene related to the saturated di-cyclic terpene pinane (p. 823). In both of these terpenes the di-cyclic arrangement is different from that in camphane and Bornylene in that the isopropyl group in forming the secondary cycle joins the meta carbons instead of the para. Now pinene, by addition of hydrogen chloride, forms a hydrochloride which has been referred to as artificial camphor. This hydrochloride is identical with the hydrochloric acid ester of Bomeol and may be converted into Bomeol by hydrolysis. Now as Bomeol can be oxidized to camphor we may thus obtain true synthetic camphor from pinene. The reactions, involving an intermediate product and then rearrangement of the secondary cycle in pinene, are as follows ... 

Cyclic terpenes monocyclic (dipentene) di-cyclic (pinene). 

The synthesis of star polymers (53) with co-methylpoly (oxyethylene) (MPEG Ain = 5000) arms and a core formed from di(cyclic phosphate) (52) has been recently reported. ... 

Semmler regards a-Santa I oI as a tricyclic compound, which, when heated to 160 w ith alcoholic potash for two hoiii s, is ruptured at the doable bond in the side chain, and the tricyclic compound is converted into di cyclic alcohol which he calls d i eye I oelt santal oL The formul for the a and /J-santalols which he suggests are as fol low s —... 

Hydrolysis (Section 20 6) Acid anhydrides react with water to yield two carboxylic acid func tions Cyclic anhydrides yield di carboxylic acids... 

When a cyclic component carries more than one identical side chain, the name of the cyclic component is followed by di-, tri-, etc., and then by the name of the acyclic component, and it is preceded by the locants for the side chains. Examples are... 

Cyclic polyoxiranes have, in recent years, provided a fruitful playground for the synthesis of fascinating structures (80T833). Most significant from the mechanistic, synthetic and biological viewpoints are the di- and tri-epoxides of benzene, all four of which (36-39) are known. 

Substituted and unsubstituted bi- or multi-cyclic mono-, di- or multi-olefins, i.e. containing condensed rings at least one of which contains a double bond. Norbomene is homopolymerised commercially whilst, as previously mentioned, ethylidenenorbomene and dicyclopentadiene are used as the cure site monomer in EPDM rubbers. 

Cyclic a,) -unsaturated ketones present a rich array of photochemical reactions, some of which are of considerable synthetic value (see Section 6.4 of Part B). For cyclohex-enones, two prominent reactions are the di-rr-methane rearrangement (path A) and the lumiketone rearrangement (path B). 

In contrast to hydrogen-type ethers, a-haloethers, both linear and cyclic, are relatively easily cleaved by anhydrous hydrogen fluoride. Bis( 1,1 -difluoroalkyl) ethers are converted to 1,1,1 -trifluoroalkanes and alkanoyl fluorides The cleavage temperature depends on the substituents present ethers having no electronegative substituents other than a-fluorines are readily cleaved below 20 °C, 3-halo-1,1-di fluoroethers require approximately 70 °C, but 2-halo-1,1-difluoroethers are prac tically resistant toward hydrogen fluoride [/I (equation 1)... 

The addition of nucleophiles to cyclic fluoroolefins has been reviewed by Park et al. [2 ]. The reaction with alcohols proceeds by addition-elimination to yield the cyclic vinylic ether, as illustrated by tlie reaction of l,2-dichloro-3,3-di-fluorocyclopropene Further reaction results in cyclopropane ring opening at the bond opposite the difluoromethylene carbon to give preferentially the methyl and ortho esters of (Z)-3-chloro-2-fluoroacrylic acid and a small amount of dimethyl malonate [29] (equation 8). 

Experiments designed to clarify the situation were carried out by Wittig and Mayer (40). It was shown that changing the molar ratio of amine (diethylamine, di- -butylamine, or diisobutylamine) to -butyraldehyde from 1 1 to 2 1 did not affect the yield of enamine (53- 64%, based on the aldehyde). Contrariwise, changing the ratio of amine (morpholine, piperidine, or pyrrolidine) to n-butyraldehyde from 1 1 to 2 1 boosted the yields from 52-57 % to 80-85 %. The authors interpret these data as indicating that the cyclic amines form aminals with n-butyraldehyde, while the open-chain do not. Infrared evidence is stated as having shown that the aminal originates not from attack of excess amine on the enamine, which is stable under the conditions of the reaction, but from the N-hemiacetal (17). 

Enamines of cyclic ketones do not form cycloaddition products, but give the mono- or dicarboxanilides (110,111). Thus the enamine (113) on reaction with 1 equivalent of phenyl isocyanate gave 160. Treatment of 113 with 2 equivalents, or 160 with 1 equivalent, of phenyl isocyanate gave the 2,6-disubstituted product (161). Mild acid hydrolysis of 160 and 161 produced the corresponding cyclohexanone(2-mono- and 2,5-di)carbox-anilides (110). 

The reaction of morpholine enamines of cyclic ketones with ethyl azodicarboxylate has also been demonstrated 56,136). The enamine (113) on reaction with ethyl azodicarboxylate can give the 2- or 2,6-bis(N,N di-carboxyhydrazino)cyclohexanones 199 and 200, respectively, on hydrolysis. 

The reduction (136) of pyridinium compounds to 1,2- or 1,4-dihydro products with complex metal hydrides or dithionite leads to cyclic di-enamines of synthetic and biochemical interest. 

Thus the reactions of cyclic or acyclic enamines with acrylic esters or acrylonitrile can be directed to the exclusive formation of monoalkylated ketones (3,294-301). The corresponding enolate anion alkylations lead preferentially to di- or higher-alkylation products. However, by proper choice of reaction conditions, enamines can also be used for the preferential formation of higher alkylation products, if these are desired. Such reactions are valuable in the a substitution of aldehydes, which undergo self-condensation in base-catalyzed reactions (117,118). Monoalkylation products are favored in nonhydroxylic solvents such as benzene or dioxane, whereas dialkylation products can be obtained in hydroxylic solvents such as methanol. The difference in products can be ascribed to the differing fates of an initially formed zwitterionic intermediate. Collapse to a cyclobutane takes place in a nonprotonic solvent, whereas protonation on the newly introduced substitutent and deprotonation of the imonium salt, in alcohol, leads to a new enamine available for further substitution. 

Solutions of alkali metals in liquid ammonia have been developed as versatile reducing agents which effect reactions with organic compounds that are otherwise difficult or impossible/ Aromatic systems are reduced smoothly to cyclic mono- or di-olefins and alkynes are reduced stereospecifically to frani-alkenes (in contrast to Pd/H2 which gives cA-alkenes). 

In the gas phase, monomeric SO3 has a planar (Di(,) structure with S-O 142pm. This species is in equilibrium with the cyclic trimer S30g in both the gaseous and liquid phases A", ... 

X0 to hydroxy compounds. Lower temperatures favor ketone formation and sterically hindered carbonyls, such as 2-thienyl t-butyl ketone, are not reduced. The sensitivity of desulfurization to steric factors is evident by the failure to desulfurize 2,5-di-i-butyl-3-acetylthiophene. The carbonyl groups of both aldehydes and ketones can be protected by acetal formation, as particularly cyclic acetals are stable during desulfurization in methanol at room temperature. " The free aldehydes give primary alcohols on desulfurization. Another method to obtain only keto compounds is to oxidize the mixtures of ketone and secondary alcohol with CrOs after the desulfurization. - Through the desulfurization of 5,5 -diacetyl-2,2, 5, 2"-terthienyl (228), 2,15-hexadecandione (229) has been obtained, which... 

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