Substitution tetralins

A range of diols and cyclic ethers were used to carry out alkylation of aromatics (benzene, toluene, xylenes, trimethylbenzenes, naphthalene) in the presence of triflic acid.204 310 In a recent study,311 various methyl-substituted benzene derivatives were alkylated with 1,4-diols [Eq. (5.117)] to form substituted tetralin derivatives in high yields. The transformations involve an intermolecular alkylation step followed by intramolecular alkylation (cyclialkylation). 2,2,5,5-Tetramethyltetrahydrofuran is similarly effective. For example, it alkylates benzene to give octamethyloctahydroan-thracene (98% yield) and reacts with naphthalene to yield octamethyloctahydrote-tracene [Eq. (5.118)]. 

Figure 8-(a) and (b) show the decoupled signals of a-CH protons in tetralins and indans, respectively. The decoupled signals at 2.76 ppm in (a) and at 2.90 ppm in (b) correspond to a-CH protons of unsubstituted tetralin and indan, respectively. The result of decoupling of Figure 8 indicates the existence of several types of orChL protons which probably are located in substituted tetralin and indan. For example, the triplet at 3.10 ppm was decoupled completely by the irradiation on the pentuplet signals at 2.05 ppm. 

The results in Figure 1 can be interpreted in terms of general ring structures with the hydrocarbon classes. The peak for the polypolar aromatic fraction at 160° C probably is caused by polar-monocyclic compounds and the peak at 240° C is probably the result of polar dicyclic compounds. The broad curve in the monoaromatics centering at 275°C is probably mainly caused by alkyl-substituted tetralins while the peaks... 

Other benzo-fused carbocycles could be prepared in moderate yield by a similar strategy. Isomerically pure 3-substituted benzocyclobutenes or 5-substituted tetralins, 211, were prepared by a five-step sequence from the appropriate a-(2-fluorophenyl)-[Pg.101]

These authors have extended this reaction to the preparation of 3-substituted benzocy-clobutenes 283 (n = 1) and 5-substituted tetralins 283 (n = 3) from a-(2-fluorophenyl)-tw-iodoalkanes 282. In a similar way as described above, the processes involve generation and cyclization of benzyne-tethered alkyllithiums via 4-exo or 6-exo, though in these cases the yields are significantly lower (Scheme 74)132. 

The rearranged clerodane (113), which has an unusual structure, is the first natural product with a substituted tetralin skeleton which could be biogenetically derived from a clerodane precursor.The rearranged clerodane (114-115) named salvipuberulin bearing a C3-C6-C6 ring system was isolated from S.puberula [106] while the other clerodane blepharolide A (116) with a different rearranged C3-C6-C6 was found in S.blepharophylla [107]. 

Friedel-Crafts alkylations. 1 -Substituted tetralins are obtained from cyclic ethers such as 2-(3-arylpropyl)tetrahydrofurans and alkyl Al-(l-hydroxy-4-arylbutyl) carbamates by treatment with TiCl. ... 

Steric and electronic effects in the chromic acid oxidation of 17 mono- and polyalkyl-substituted tetralins have been fully examined. As perhaps expected, preferential oxidation occurs at benzylic methylene position (s) para to the alkyl substituent in the benzene ring. 

Initially, the Bradsher cycloaddition reaction was used to gain greater understanding of the Diels-Alder reaction. More recently it has found utility in the constuction of carbon frameworks that provided novel entries into the synthesis of natural products. For example, the Bradsher cycloaddition reaction has been reported on the use of isoquinolinium salts for the stereocontrolled synthesis of substituted tetralins. Reaction of... 

Sodium-ammonia reductions of the cis-and trons-divinylcyclopropanes (2S1) and (252) do not produce identical product mixtures, as is observed for cis- and trans-divinylcyclobutanes. The stereospecificity exhibited by (251) in producing only trans-propenylcyclopentenes (Scheme 37) could be due to charge-transfer stabilization in the anion radical (253). The reduction of exo-7-phenylbenzo[2,3]bicyclo[4,l,0]-heptene (Na-NH ) has now been shown to give 2-benzyltetralin, and not 4-phenyl-benzocycloheptene as previously reported a series of 2-substituted tetralins and their 4-oxa-analogues have been obtained by this procedure. Reduction of (93 X = Cl)... 

A highly electrophilic phosphite gold(I) catalyst was applied to the intramolecular allene hydroarylation reaction to give a vinyl-substituted carbocycle [17], This cyclization proceeds effectively in cases where the aryl groups are electron-rich arene nucleophiles. A dimethoxybenzene bearing an allene group furnished a vinyl-substituted tetralin derivative in 85% yield (Scheme 18.18). From the mechanistic... 

---