Carbocyclic compounds, synthesis

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. 

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... 

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. 

Cycloaddition reactions can provide excellent means of producing carbocyclic compounds, and there are many good examples of the application of this approach to the synthesis of functionalized cyclohexanes from carbohydrates [4],... 

Cycloaddition reactions are valuable for the synthesis of carbocyclic compounds. Each of the following compounds can be formed by either a [4 + 2] or [2 + 2] cycloaddition as a last step in the synthesis. Draw the structures of the reagents you think would undergo cycloaddition to give the compounds shown. 

A number of different approaches for conversion of carbohydrate derivatives into functionalised carbocyclic compounds have been reviewed (34). Our approach towards the synthesis of this type of compounds has been the radical initiated carbocyclisation of co-bromo-G)-deoxy-(x,p-unsaturated aldonolactones. 

As a conclusion, it should be emphasised that 2,3-unsaturated aldonolactones, in which a radical can be generated at the primary position, are useful starting materials for the stereospecific synthesis of highly functionalised, optically pure carbocyclic compounds. 

Especially in the case of enaminones bearing a substituent at the nitrogen, side reactions90 become predominant and open a method for synthesis of carbocyclic compounds, which can be aromatized to substituted diphenyl derivatives91. An interesting azocine ring is produced in a side reaction91 (equation 63). 

Applications of the Wittig reaction in the synthesis of heterocyclic and carbocyclic compounds... 

Synthesis of heterocyclic and carbocyclic compounds via alkynyl, allyl, and propargyl organometallic cyclopentadienyl iron, molybdenium and tungsten complexes 00CRV3127. 

Sulfur ylides in the synthesis of hetero- and carbocyclic compounds 01UK744. 

The synthesis of carbocyclic compounds from acyclic precursors can be accomplished by a sequence of radical reactions, where thiyl radicals act as catalysts. As an example, the generation of homoallyl radicals through the addition of phenyl-thiyl radical to the double bonds of vinyl cyclopropanes results in the multi-step synthesis of cyclopentanoids [62]. The mechanism is shown in Scheme 13. Feldman and coworkers have demonstrated that the success of this strategy is based on the coupling of vinyl cyclopropanes with the electronically complementary functionalized alkenes. A judicious choice of substituents R and X accelerates the rate limiting step (c). 

The success of the strategy is further applied for the synthesis of carbo-and spiro-aimulated aromatic compounds [146,147] by the intramolecular cyclization of silyl enolethers to PET-generated arene radical cations. Two types of carbocyclic compounds (170 and 173), varying in ring sizes, may be synthesized [146] starting from the same ketone (i.e., 169), as two types of silyl enol ethers can be produced using either thermodynamic or kinetic enolisation procedures. The core spiro structure (177) of the anticancer antibiotic ffed-ericamycin is also prepared [147] by the PET cyclization of 176 (Scheme 36). 

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