Carbocyclic compounds

Examples of natural carbocyclic compounds with rings of various sizes and shapes. The source and special features of each structure are indicated below it. 

A ring with two side chains, one of which is branched 

A bicycUc molecule one would have to break two bonds to make it acyclic 

A male sex hormone in which several rings of common sizes axe fused together that is, they share two adjacent carbon atoms 

Cycloaddition to a-P-unsaturated carbonyl systems represented by different carbohydrate enones yield annulated osides. These bicyclic molecules are used for synthesis of carbocyclic systems using the stereochemical information issued from sugar 

A stereoselective photochemical addition of diazomethane to unsaturated uronate 40 undergoes a pyrazoline derivative 41 which, after photolysis, leads to cyclopropano- 

These annulated bicyclic systems are of interest for further synthesis of complex macrolide antibiotics. 

Benzene reacts with xenon difluoride in the vapour phase at 200 °C to give a 60% yield of fluorobenzene, and naphthalene and 2-fluoropyridine may also be fluorinated with this reagent. The formation of phenyl benzoate from benzoic acid and benzene in the presence of xenon difluoride (Vol. 2, p. 352) has been discussed in more detail and the reaction has been extended to substituted benzoic acids.  

Althou silver(n) fluoride and potassium tetrafluoroargentate(in) (KAgF4) are slightly less active fluorinating agents than cobalt(in) fluoride, the reaction of either silver compound with benzene at 300—380 °C gives mainly dodecafluoro-cyclohexane (see also p. 6). A similar result is obtained from the complex fluoride at 120°C, but at this temperature silver(n) fluoride itself affords significant 

The electrochemical fluorination (Simons cell anhydrous HF electrolyte, sometimes with the addition of NaF to improve conductivity) of benzene, fluoro- and chloro-benzene, w-dichlorobenzene, anisole, o-chloroanisole, thiophenol, p-chloro-thiophenol, iw-thiocresol, 2-chloropyridine, and 3-chloropyridine has been examined in detail (see also p. 212). Benzene and fluorobenzene give mainly dodecafluoro-cyclohexane, but a low yield of chloroundecafluorocyclohexane is obtained from chlorobenzene, and the ethers give fully saturated perfluoroethers with some cleaved products cleavage of the thiophenols leads to extensive formation of SFe. Mixtures of perfluoro-alicyclic and -aliphatic tertiary amines are obtained by similar fluorination of AW-dialkylanilines [PhNEta and PhNMeR (R = Et, Pr, or Bu )] and the three A A -dimethyltoluidines. The relatively new technique (Vol. 2, p. 353) of controlled fluorination at a platinum anode in acetonitrile con-+ - 

Plashkin, L. Pushkina, Yu. P. Dolnakov, and S. V. Sokolov, Zhur. org. Khim., 1973, 9, 2525 Novosti Electrokhim. Org. Soedinenii, Tezisy Dokl. Vses. Soveshch. Electrokhim. Org. Soedinenii, 8th 1973 (Publ. 1973), 181 IChem. Abs., 1975, 82, 36 587d). 

Physical constants of several partially fluorinated biphenyls (up to the 2,2, 3,4, -5,5, 6-heptafluoro-compound), obtained by a range of classical methods including the Friedel-Crafts, Ullmann, and Balz-Schiemann reactions, have been reported, and 1,8-difluoro- or 1,4,5-trifluoronaphthalene may be obtained by conventional routes (nitration, reduction, diazotization) from 1,8-diamino- or 1,5-difluoro-naphthalene, respectively.  

Reagents i, OSO4. NMNO ii. (MeO)3P(0)CH2U Hi Dess-Martin periodinane iv, BH3.OMS v, PCC vi, K2CO3,18-crown-6,60 °C. 

A number of radical cyclizations of carbohydrate-derived intermediates have been reported this year for synthesis of carbocycles. One interesting example of tandem radical cyclizations involves the first example of a product derived by a formal radical [2+2+2] cycloaddition. Thus, reaction of 7 using triphenyltin 

Carbohydrate Chemistry, Volume 30 The Royal Society of Chemistry, 1998 

Reagents i, Ph3P=CHC02Me ii.TbdmsCI, ImH iii, BusSnH, AIBN. 

Reagents i, HCCMgBr ii.HslOg iii, NH20Bn iv, PhaSnH, EtsB. 

The cyclopentene 7 can be prepared from 2,3,5-tri-O-benzyl-D-ara-binofuranose (sugar carbons numbered) in five steps and high overall yield (Vol. 33, p. 241 see also Org. Lett, 1999,1,1463). This intermediate has been used to prepare (—)-pentenomydn (8) in a further five steps, the first of which was a hydroboration-oxidation which occurred with 2 1 regioselectivity in the desired sense.  

When the biscobalthexacarbonyl complex 17, prepared from 2-acetoxy-3,4,6-tri-O-acetyl-D-glucal, was treated with NMNO, a Pauson-Khand reaction occurred to give the fused cyclopentenone 18 in virtually quantitative yield. Treatment of 17 with triflic add caused epimerization at C-1, and the stereoisomer also underwent Pauson-Khand cyclization eflfidently.  

Reagents i, (Ph3P)4Pd (cat.). EtaN, toluene, reflux ii, TBAF 

Reagents i, MeLi ii, PCC, Mol. sieves iii, vinyl-Li, CuCN, —78 C, then CHgO, THF 

An intramolecular Wadsworth-Emmons reaction was used as a key step in the synthesis of (I), an inhibitor of glyoxylase I isolated from 

. derived from D-Mannose. Similar chemistry was used in an improved 

There has been further activity in the use of sugars as precursors for the A ring of anthracyclinones. The aldehyde (3), previously reported (Vol. 18, p, 248), has been prepared by an improved procedure and converted into (4), a suitable intermediate for an AB + CD approach to the tetracycle. Similar routes to those described earlier (Vol. 18, p. 248) have been used in the synthesis of (5), containing the key tertiary carbinol function, from diiso-propylidene glucose via a Marschalk reaction, and earlier work has 

Cycloaddition reactions have been used for the annulation of carbocyclic rings onto carbohydrate templates. The butenolide (6), derived from D-ribonolactone, gave the potential prostacyclin syn-thon (7) via reaction with butadiene and the chrysanthemic acid 

A conceptually similar cyclization was used to form the 4-membered 

A review on the synthesis of mevinic acids such as compactin (1) 

A Michael reaction-Claisen condensation involving the previously reported intermediate (4) derived from galactose (see 

Diels-Alder reaction between a glucose-derived enone and butadiene, followed by Ferrier rearrangement, gave (8) (glucose numbering shown), which corresponds to the AB-ring stereochemistry 

The bicyclic system of the mycotoxin diplodiatoxin (9) was established by intramolecular Diels-Alder reaction, with the 

The simple chiral building block (12) has been been prepared from D-mannitol, via (R)-isopropylidene glyceraldehyde, using a Wadsworth-Emmons reaction the unsaturated synthon (13) was also prepared by a variant on the route.Using (12) prepared in a 

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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. 

Acyloins are useful starting materials for the preparation of a wide variety of heterocycles (e.g., oxazoles and imidazoles ) and carbocyclic compounds (e.g., phenols ). Acyloins lead to 1,2-diols by reduction, and to 1,2-diketones by mild oxidation. 

Gutman and S. J. Cyvin, Introduction to the Theory of Benzenoid Hydrocarbons, Springer-Verlag, Berlin, 1989. 3 Lloyd, Nonbenzenoid Conjugated Carbocyclic Compounds, Elsevier, Amsterdam, 1984. 

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). 

Furthermore, intramolecular cyclization of acyclic chiral imines, in which the imine and the enone groups are separated by alkyl chains, yield optically active cyclohexane and cyclopentane derivatives. /ra .v-l,2-Disubstitutcd carbocyclic compounds are exclusively or predominantly formed with diastereomeric ratios in the range 80 20 100 0, strongly dependent on the conditions used to induce cyclization, i.e. heat, pressure or Lewis acid (MgBr2) catalysis227. 

By the radical pathway l, -diesters, -diketones, -dienes or -dihalides, chiral intermediates for synthesis, pheromones and unusual hydrocarbons or fatty acids are accessible in one to few steps. The addition of the intermediate radicals to double bonds affords additive dimers, whereby four units can be coupled in one step. By way of intramolecular addition unsaturated carboxyhc acids can be converted into five raembered hetero- or carbocyclic compounds. These radical reactions are attractive for synthesis because they can tolerate polar functional groups without protection. 

Metal TT-Complexes Formed by Seven- and Eight-Membered Carbocyclic Compounds, 4,353... 

It is clear from the preceding comments that there is no absolute distinction between the oxygenase activities mediated by dioxygenases. This is even less clear for heteroarenes than it is for carbocyclic compounds. An illustrative example is provided by Pseudomonas putida strain 86 in which 8-hydroxy-quinol-2-one is produced from quinol-2-one (Rosche et al. 1997). 

The degradation of xanthone by Arthrobacter sp. strain GFBIOO closely resembled the pathways used for carbocyclic compounds. In a yeast-supplemented medium, initial dioxygenation to the 3,4-dihydrodiol was followed by dehydrogenation to 3,4-dihydroxyxanthone and extradiol ring fission to a coumarin and subsequent production of 2,5-dihydroxybenzoate (Figure 10.38) (Chen and Tomasek 1991 Tomasek and Crawford 1986). 

In Entry 3, the trans stereochemistry arises at the stage of the protonation of the enolate. Entry 4 gives rise to a cis ring juncture, as does the corresponding carbocyclic compound.59 Models suggest that this is the result of a steric differentiation arising from the axial hydrogens on the a-face of the molecule. 

The reaction has been developed for the synthesis of both oxygen heterocycles and carbocyclic compounds.72... 

Moreover, the authors were able successfully to apply this process to the synthesis of the antibiotic (+)-CP-263,114 (2-912) (Scheme 2.203) [454]. Transformation of the bromide 2-908 into the vinyl Grignard reagent 2-909, followed by addition to the ketone 2-910, led to the bridged carbocyclic compound 2-911 which was then transformed into the target compound within a few steps. 

A regio- and diastereoselective Pd-catalyzed domino silastannylation/allyl addition of allenes 6/1-236 containing a carbonyl moiety with Bu3Sn-SiMe3 6/1-237 is described by Kang and coworkers [117]. The reaction allows the synthesis of hetero-and carbocyclic compounds with a ring size of five and six. It can be assumed that... 

Carbocyclic compounds containing an unsubstituted exocyclic methylene group give 1,2-diazetidines with PTAD. Methylene adamantane gives the adduct 47,8 5 and the methylene cyclopropane (48, R = H) gave the 1,2-diazetidine 49.86 The phenyl-substituted compound (48, R = Ph) behaved similarly to styrene and gave a 2 1 adduct with PTAD (see Section IV,D,1). 

This chapter deals with thermal ring-closure reactions of dienes and polyenes resulting in carbocyclic compounds the formation of heterocycles is mentioned only occasionally. The account is highly selective, concentrating on recent work, since two comprehensive general reviews have appeared1,2. Other pertinent reviews are cited at appropriate places in the text. 

GeH2 13 C and 73 Ge NMR. Chair conformation as determined from spectroscopy, in accordance with molecular structure calculations, similarly to the analogous carbocyclic compound. Introduction of bulky substituents results in a preferred boat conformation. 60... 

Syntheses of Carbocyclic Compounds (1.V.2.V )-2 (.V )-Amino(4-metho-xyphenyl)methyl]cyclopropan-l-ol 392 (Scheme 1.45) has been prepared by a stepwise procedure involving a 1,3-dipolar nitrile oxide cycloaddition to allyl alcohol followed by a constmction of the cyclopropa d isoxazole system, and reduction of the bicycle (436). 

Feringa and co-workers described the tandem addition-aldol cyclization protocol leading to the formation of 6,6-, 6,7-, and 6,8-annulated bicyclic systems (Scheme 68).39 Using Cu(n)-29 as catalyst and functionalized organozinc reagents as nucleophiles, the conjugate addition reaction followed by aldol cyclization can offer highly enantioselec-tive annulation products (up to 98% ee). This method can be used in the synthesis of carbocyclic compounds, such as steroids, terpenes, and other natural products. 

Reactions of Titanium Carbene Complexes with Carbon—Carbon Double Bonds Table 14.1. Preparation of carbocyclic compounds from alkenyl thioacetals. 

The cationic cyclization of polyenes to give multi-ring carbocyclic compounds with many sterically defined centres is one of the more remarkable examples... 

C NMR spectroscopy of 1,7-dioxa- (314), l-oxa-7-thia- (315), and 1,7-dithiaspiro[5.5]undecane (316) and many of their derivatives, with special emphasis on stereoelectronic and steric effects governing the configurational and conformational properties of these compounds (484-486). This work showed that chemical-shift parameters developed for six-membered carbocyclic compounds in chair conformations (149) could be applied successfully only to sulfur and not to oxygen heterocycles (486). 

Whereas alkylation of activated methylene systems by classical methods produces a mixture of mono- and dialkylated products, with the latter frequently predominating, phase-transfer catalytic procedures permit better control and it is possible to obtain only the monoalkylated derivatives. Extended reaction times or more vigorous conditions with an excess of the alkylating agent lead to dialkylated products or, with dihaloalkanes, carbocyclic compounds as the technique mimics dilute concentration conditions, e.g. the resonance stabilized cyclopentadienyl anion, generated under solidiliquid two-phase conditions, or under liquiddiquid conditions, reacts with 1,2-dihaloethanes to form spiro[2,4]hepta-4,6-diene (70-85%) [1-3]. Reaction with dichloromethane produces bis(cyclopenta-2,4-dien-l-yl)methane (60%) [4],... 

In principle, the same "heuristic principles" which apply to carbocyclic compounds are also applicable to heterocyclic systems [29]. However, it must be kept in mind that ... 

The same "heuristic principles" which are applied to carbocyclic compounds also hold true for simple heterocyclic compounds containing one heteroatom. However, in the case of bridged heterocyclic molecules a modified strategic bond selection must be applied. Besides the strategic bonds which meet Corey s six rules, the bonds directly attached to nucleophilic heteroatoms -such as O, S and N-are also strategic Cf. heuristic principle HP-7), provided that they satisfy rules 2B, 4, 5 and 6. For instance, in compound 31a besides the five strategic bonds determined by rules 1-6 (cf. compound 26), the sixth darkened C-N bond in 31b is also a strategic bond. 

A selection of preparations of carbocyclic compounds by RCM is given in Table 3.18. 

D. Lloyd, Non-Benzenoid Conjugated Carbocyclic Compounds, p. 67. Elsevier, Amsterdam, 1984. 

As polycyclosiloxane systems the skeleton of which is made up of intermittent silicon and oxygen atoms. These atoms are numbered by the method used for analogously built carbocyclic compounds in which the number of carbon atoms... 

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