Methylnaphthalene, cyclization

MethyUndanes, 20 281 Methylindene, cyclization, 28 298 Methylnaphthalene, cyclization, 28 298, 299 Methyl-N-phenylcarbamate synthesis, 41 226-227... 

The primary products of -pentylbenzene cyclization are 1-ethylindan, 1-ethylindenes, and 1-methylnaphthalene. Secondary (consecutive) isomerization may produce dimethylindans, 2-ethylindan, the corresponding in-denes, and 2-methylnaphthalene ... 

The primary products of the cyclization of 2-phenylpentane are cis- and /ra j-l,3-dimethylindans, 1,3-dimethylindene, and 1-methylnaphthalene ... 

Neither C5- nor C6-cyclization involve carbonium-ion intermediates over platinum metal. The rates of the -propylbenzene - indan reaction (where the new bond is formed between a primary carbon atom and the aromatic ring) and the n-butylbenzene- 1-methylindan reaction (which involves a secondary carbon atom) are quite similar (13). Furthermore, comparison of the C6-cyclization rates of -butylbenzene and n-pentylbenzene (forming naphthalene and methylnaphthalene, respectively) over platinum-on-silica catalyst shows that in this reaction a primary carbon has higher reactivity than a secondary carbon (Table IV) (29). Lester postulated that platinum acts as a weak Lewis acid for adsorbed cyclopentenes, creating electron-deficient species that can rearrange like carbonium ions (55). The relative cyclization rates discussed above strongly contradict Lester s cyclization mechanism for platinum metal. 

On the other hand, the n-pentylbenzene - methylnaphthalene reaction proceeds through C6H5-CH2-CH2-CH2-C+H-CH3, a secondary carbonium ion. As a consequence, acid-catalyzed cyclization produces both five- and six-membered rings. The possible carbonium ion intermediates leading to five- or six-membered ring closure may have similar structures (e.g., both are secondary carbonium ions, as in the case of n-pentylbenzene). If so, acid-catalyzed cyclization favors six-membered ring products, as shown by the k5/k6 ratios (Table IV). 

A further example of the use of 2//-thiopyrans as surrogates for m-substituted dienes involves the use of the protected 3,4-dihydio-3-(3-oxobutyl)A//-thiopyranA-onc, 3-[2-(2-methyl-l,3-dioxolan-2-yl)ethyl]-4-[tris(l-methy-lethyl)silyl)oxy-2//-thiopyran 328 as an equivalent of l-ethenyl-2-methylcyclohexene in Diels-Alder reactions. The thiopyran reacted with various maleimides to yield the endo cycloadducts and with methyl propenoate to give the exo adduct under either thermal or Lewis-acid-catalyzed conditions. In the latter case concomitant release of the protected ketone functions occurs, acid-catalyzed cyclization of which generates a fused cyclohexenone ring (Scheme 67). Desulfurization, preferably before the aldol cyclization, leads to derivatives of 2,3,4,4a,5,6,7,8-octahy-dro-4a-methylnaphthalenes < 1997CJC681 >. 

The dihydro-cyclopentano-phenanthrene (120) has been synthesized (Scheme 9) from 2-acetyl-3-methylnaphthalene (115), which was converted into the fur-furylidene derivative (116). Treatment with acid afforded the expected dioxo-heptanoic acid (117), which on treatment with base provided the cyclopentenone (118). This keto-acid (118) readily underwent cyclization when boiled with acetic anhydride, furnishing ll-acetoxy-15,16-dihydro-7-methylcyclopenta[a]-phenanthren-17-one (119a). Deoxygenation at C(ll) was performed through... 

To gain a linear annelation to an anthracene by blocking up position 1 in (71) with a methyl group, we synthesized the aminonitriles (74a, b) by condensation of (7b), or (7i), with l-methylnaphthalene-2-acetonitrile (73). The latter was obtained from l-methyl-2-naphthoic acidso in three steps to give an overall yield of 60%. All attempts to enforce the cyclization of (74a) or (74b), however, were defeated. An uncontrolled decomposition of (74a, b) to tarry products takes place above 300°44 ... 

Photo-addition of alkenes to A methylnaphthalene dicarboxamides in benzene has been studied. The structure of the arene moiety in the imide was important in determining the reaction path. Mainly cyclobutane and oxetan formation occurred. The dicarboximide (342) undergoes photochemical cyclization with incorporation of methanol to yield the two products (343) and (344) in 55 and 16% respectively. This type of cyclization appears to be quite general for such systems and is also reported for the imides (345) and (346). A variety of products resulting from aminolysis, reduction, and radical coupling is produced on irradiation of the phthalimide (347) in diethylamine. ... 

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