1-Tetralone, //-keto esters

Reactions of carbocyclic P-keto esters, sulfonium ylides and enamines with activated alkynes such as DMAD are known to result in formation of (n + 2) ring expanded products. In a study of the analogous reactions of carbocyclic p-keto phosphonates, it was found that in the cases of the simple cyclic P-keto phosphonates 1, ring expansion occurred to give 2 in reasonable yield. Extension of the method to the tetralone 3, however, led to formation of two products, the "expected" (n + 2) ring expansion product analogous to 2 (37%), and the lactone 4 (29%). 

By the simple procedure of passing dispersed air through a suspension of ff2-diethylbenzene, 1% chromia, and 4% calcium carbonate at 130° for 40 hours, a 50% yield of m-ethylacetophenone is obtained. Likewise, aromatic esters, acetophenones, and halogenated benzenes containing alkyl groups yield the corresponding keto esters, diketones, and halo ketones, respectively. Manganese dioxide catalyst has also been used. Tetralin can be oxidized to a-tetralone with dispersed air in the absence of a catalyst (56%). ... 

Access to optically active 2-fluoro-l-tetralone 53 was achieved using the same palladium-mediated cascade reaction [30]. The catalytic enantioseiective decarbox-ylative protonation of 2-fluoro benzyl P-keto ester 54 in the presence of 30 mol% of quinine 20 afforded enantioenriched (S)-tetralone 53 in 65% ee (Scheme 7.24). The reaction was very sensitive to the nature of the palladium catalyst used. Furthermore, a minor amount of defluorinated product was observed. Several other cinchona derivatives were tested including analogues of cinchonine described by Brunner in organocatalytic EDP (see Section 7.5.3), but these chiral inductors afforded low selectivities (<30% ee). 

This reaction, similar to the reductions of other cyclic ketones, shows higher selectivity when nonfermenting baker s yeast is used 89,155. Bicyclic /J-keto esters from 1- or 2-tetralone derivatives are also accepted as substrates and are transformed selectively by yeast89,151 153. 

Pyrrolidine added to a soln. of 127 g. 5-methoxy-2-tetralone in benzene, refluxed 7 hrs. in a flask provided with a water separator, the benzene removed by distillation, the residue dissolved in dioxane, heated to reflux, ethyl bromo-acetate in dioxane added, and refluxing continued 22 hrs. under Ng 178 g. keto ester. R. W. Guthrie et al., Coll. 31, 602 (1966). 

The asymmetric allylation reaction offers a very easy access to chiral quaternary centers. The first example of catalytic asymmetric alkylations of a-substituted -keto esters using 1 in the presence of pocket ligand (l/f,2/f)-his[(diphenylphosphino)-benzamido]cyclohexane in high selectivity has been reported. The tetralone system showed high selectivity, with the allylated... 

The Behenna-Stoltz protocol was soon applied to a-fluoroketones. As shown in Scheme 5.26, the silyl enol ethers 80 of 2-fluoro-indanone, tetralone-, and ben-zosuberone can be reacted with allyl or methallyl carbonate to give the tertiary a-fluorinated ketones 81 in 83-95% ee [43]. The procedure that was also applied to an allylation of 4,4-dimethyl-6-fluorocyclohexenone offers an alternative to the enantioselective fluorination of enolates on the one hand and the decarboxylative allylation of fluorinated P-keto esters on the other hand vide infra). 

Derivatives of the type of (250) have also been obtained by the use, as the AB component, of unsubstituted oj-tetralone or, as the D component, of acetylcyclohexene [359, 361, 362, 364-367]. Attempts to use acyclic keto esters in the reaction with (8) and their subsequent cyclization were unsuccessful [368] likewise, bicyclie ketones not containing an aromatic... 

Synthesis of the tricyclic homolog (253 R =Me) was carried out from the corresponding methoxytetralone (184 R =Me) by a method similar to that described previously [846]. The methoxycarbonylation and methylation of the initial tetralone led to compound (252), from which the methyl ketone (250 R = Me) was obtained by decarboxylation. Its condensation with acrylonitrile led to the cyanoketone (251), and hydrolysis and methylation of the latter gave the keto ester (254), the conversion of which into the corresponding methyl ketone and cyclization enabled the tricycle BCD fragment (253 R = Me) to be obtained. In this example, the formation of ring A was not studied. 

A carboxyl functionality can be introduced at C-2 by this method an a-keto acid or ester reacts with a chalcone under the usual conditions (68CB2215, 82JOC492), whilst benzylidene-l-tetralone affords the naphthopyrylium salt (669) (82JOC498). 

The optimised conditions were then applied to a range of cyclic a-alkyl and a-benzyl substituted P-keto allyl esters to generate the corresponding a-tertiary ketones in good yields and excellent enantioselectivities. Interestingly the fused aromatic substrates such as tetralone 102 gave the opposite sense of stereoinduction in the resulting tertiary product (105), compared to the monocyclic compounds such... 

---