Decaline synthesis

For this particular cis-decalin synthesis, it was eventually found that best results were obtained with the corresponding vinyl triflates and Pd(BINAP) (Scheme 8G.5) [l 3). As illustrated in these examples, the reaction of unsaturated triflates under cationic conditions typically is done in a nonpolar solvent, in the presence of an inorganic base such as K2C03 or a tertiary amine Pd(OAc)2 and Pd dba CHC have been the most widely used palladium sources. 

The usefulness of this cis-decalin synthesis was demonstrated by an enantioselective synthesis of the sesquiterpene (+)-vemolepin 6.4 (Scheme 8G.6). Thus, Heck cyclization of the... 

The general method described in Sect. 4.1.1 for decalin synthesis has also been applied to the synthesis of 6,5-ring systems through the formation of hydrindans (Scheme 6) [32]. 

A further d.v-decalin synthesis starts from an oxonium iona1, The least alkylated end is attacked regioselcctively by the central double bond and the use of an electron-rich terminator is required (proton loss is nonregioselective). 

CoF is used for the replacement of hydrogen with fluorine in halocarbons (5) for fluorination of xylylalkanes, used in vapor-phase soldering fluxes (6) formation of dibutyl decalins (7) fluorination of alkynes (8) synthesis of unsaturated or partially fluorinated compounds (9—11) and conversion of aromatic compounds to perfluorocycHc compounds (see Fluorine compounds, organic). CoF rarely causes polymerization of hydrocarbons. CoF is also used for the conversion of metal oxides to higher valency metal fluorides, eg, in the assay of uranium ore (12). It is also used in the manufacture of nitrogen fluoride, NF, from ammonia (13). 

The chiral copper reagent 24 is an effective catalyst not only for intermolecular, hut also for intramolecular Diels-Alder reactions, as shown in the following schemes (Scheme 1.41, 1,42, 1.43). Synthetically useful octalin and decalin skeletons were synthesized in high enantio- and diastereoselectivity. The synthetic utility of this intramolecular Diels-Alder reaction has been demonstrated hy a short total synthesis of isopulo upone [23, 33d]. 

Similarly, efficient tetracyclization (MeAlCl2-promoted) of the bis-allylic silane/ bis-epoxide 97 constitutes the key step in the synthesis of (+)-a-onocerin. In this case, because of the presence of the bis-allylic silane group, a double bis-annula-tion occurs, with the formation of the ethylene-bridge linked bis-decalin system present in the target compound (Scheme 8.26) [46],... 

An intramolecular cycloaddition reaction of 117 is the crucial step in the synthesis of the highly functionalized decalin [115] moiety of azadirachtin 119. 

Decalin unit 121, an intermediate in the total synthesis of compactin, has been prepared by intramolecular cycloaddition reaction [117] of trienone-carboxylic acid 122 carried out under either thermal conditions or microwave irradiation. The desired cxo-adduct 123 was the major stereoisomer (Equation 2.34). Similar results were observed in the cycloadditions of the corresponding esters. 

Synthesis of decalin synthons of bioactive terpenoids Lewis-acid-cataiyzed Dieis-Aider reactions [109]... 

The formation of the naphthalene (73) from the bis-ylide (72) and diethyl ketomalonate involves an unusual olefin synthesis on the carbonyl of an ester group. The methylene-pyrans (75) were formed when the diethyl malonates (74) were refluxed with j3-keto-ylides in xylene or decalin. Possible intermediates are the ketens (76) and the allenes (77). Addition of ylide to the allenes gives the betaines (78) which form methylene-pyrans either directly or via acetylenes as shown. 

In a series of publications over the past few years, the group of Barriault has reported on microwave-assisted tandem oxy-Cope/Claisen/ene and closely related reactions [175-178], These pericyclic transformations typically proceed in a highly stereoselective fashion and can be exploited for the synthesis of complex natural products possessing decalin skeletons, such as the abietane diterpene wiedamannic... 

The synthesis of the decalin unit of compactin (59), a potent competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, which acts as an effective hypocholesterolemic agent, was planned to incorporate an intramolecular Diels-Alder reaction (Scheme 9.15) [57]. 

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