Tetralins rearrangement

The catalytic system used in the Pacol process is either platinum or platinum/ rhenium-doped aluminum oxide which is partially poisoned with tin or sulfur and alkalinized with an alkali base. The latter modification of the catalyst system hinders the formation of large quantities of diolefins and aromatics. The activities of the UOP in the area of catalyst development led to the documentation of 29 patents between 1970 and 1987 (Table 6). Contact DeH-5, used between 1970 and 1982, already produced good results. The reaction product consisted of about 90% /z-monoolefins. On account of the not inconsiderable content of byproducts (4% diolefins and 3% aromatics) and the relatively short lifetime, the economics of the contact had to be improved. Each diolefin molecule binds in the alkylation two benzene molecules to form di-phenylalkanes or rearranges with the benzene to indane and tetralin derivatives the aromatics, formed during the dehydrogenation, also rearrange to form undesirable byproducts. 

Autoxidation may in some cases be of preparative use thus reference has already been made to the large-scale production of phenol+ acetone by the acid-catalysed rearrangement of the hydroperoxide from 2-phenylpropane (cumene, p. 128). Another example involves the hydroperoxide (94) obtained by the air oxidation at 70° of tetrahydro-naphthalene (tetralin) the action of base then yields the ketone (a-tetralone, 95), and reductive fission of the 0—0 linkage the alcohol (a-tetralol, 96) ... 

Methylindan and Butyl benzene. Methylindan may be formed by structural rearrangement of Tetralin with no net change in its hydrogen content. However, in E10, the protium content of the methylindan, 41.4 atom % 1H, was much greater than that of the tetralin, while in El9 the protium content of the methylindan, 13.2 atom % 1H, was only slightly greater than that of the Tetralin. 

Tetralin has been shown to undergo thermal dehydrogenation to naphthalene and rearrangement to methyl indan in either the absence or presence of free radical acceptors [ 1, 2]. The presence of free radical acceptors usually accelerates the rearrangement reaction. Even with alkylated Tetralins>... 

DHN. Apparently DHN both thermally dehyrogenates to naphthalene and disproportionates to Tetralin and naphthalene. In all of the runs, there was a sizable amount of hydrogen released when the reactors were opened. When DHN was heated at 450°C for either 15 or 180 minutes, the ratio of naphthalene to etralin was 1.8. Increased methyl indan formation occurred with time. With the introduction of dibenzyl, the anticipated [2] increased isomerization of T etralin to methyl indan occurred. These results suggest that the rearrangement of hydroaromatics does not proceed through the dihydro-... 

Sym-octahydrophenanthrene (HgPh) would be expected to follow the same rearrangement-dehydrogenation reactions as Tetralin, except with more isomer and product possibilities. The reactions shown in Figure 1 illustrate the many structures expected from sym-HgPh in the presence of free radical acceptors. Unlike Tetralin, hydrophenanthrenes have multiple structures which each, in turn, form various isomers. The amounts of these isomers are dependent upon the type of hydrogen-transfer reactions and the environment of the system. 

The retrosynthetic concept of the Nicolaou group is shown in Scheme 22. The target molecule 36 is disconnected via an IMDA cyclization of the diene quinone precursor 138, which would be generated from the tetraline derivative 139 using Wittig chemistry followed by aromatic oxidation. A Claisen-type rearrangement would provide access to 139 whereby the side chain required for the rearrangement of 140 would be introduced by 0-acylation. The core of 141 would be formed via an intermolecular Diels-Alder reaction between diene 142 andp-benzoquinone 130 [42]. 

The addition of 1-lithiocyclopropyl phenyl sulfide to paraformaldehyde was the first step of an efficient synthesis of cyclobutanonc (8).169 The adduct 7 was rearranged with/Moluenesulfonic acid monohydrate in a mixture of tetralin and water while the liberated benzenethiol was trapped with mercury(II) chloride. 

Oxetanes have also been used as alkylating agents in the Friedel-Crafts reaction for example, 2-isopropyloxetane was reacted with benzene in superacidic trifluoromethanesulfonic acid (TFSA) to give a mixture of alkylated aromatic products (Equation 9) <2003CAL1>. The main product of the reaction was the tetralin derivative 46 which could be isolated in up to 75% yield. Other notable side products are shown, resulting from monoalkylation or other skeletal rearrangements. 

El spectrum of tetralin. The complete aromatization through the loss of four hydrogen atoms is indicated by the presence of the peak at m/z 128. The most abundant ion results from the loss of ethylene. As in the case of most cyclanics, an intense ion is observed at (M-15), derived from the loss, following a rearrangement, of a methyl group. The typical ions benzylium (91) and phenylium (77) lose 26 Da, acetylene, and produce fragments at m/z 65 and 51, respectively. 

Alkyl-2-phenylquinazolines 9 are readily available by reaction of 5,S -dimethyl-A-(A-aryl-benzimidoyl)sulfimides 7 with enamines 8 in refluxing Tetralin (1,2,3,4-tetrahydronaphthalene). The mechanism of quinazoline ring formation probably involves a thermal cleavage of the imidoylsulfimides into imidoyl nitrenes, nitrene addition to the enamine double bond and subsequent rearrangement of the aziridine intermediate thus formed to the final product 9. Small amounts (10-15%) of 4-unsubstituted quinazolines 10 are obtained as byproducts. The formation of these byproducts involves a known intramolecular rearrangement of the benz-imidoylsulfimides employed. ... 

One outstanding reaction related to Friedel-Crafts alkylation is the sliding cyclohexane rearrangement mediated by ZrCU as shown in Eq. (13) [14]. When tetralin 29 was stirred with ZrCU at ambient temperature for 2 days isomerized product 32 was obtained in high yield. The mechanism in which intermediates 30 and 31 are proposed involves the ambivalent, hard and soft Lewis acidic character of zirconium. 

The scrambling of 12% deuterium to the 2-position is consistent with a relative reactivity of hydrogen at the 1-position to hydrogen at the 2-position of (very roughly) 3 1 toward hydrogen abstraction. Further evidence for the formation of 2-tetralyl radical comes from the observation of 1-methylindan from the thermal rearrangement of tetralin. Work in our laboratory has shown that 1-methylindan results from the 1,2-phenyl migration of 2-tetralyl radical and does not occur via 1-tetralyl... 

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]. 

Cycloalkylations with primaiy and secondary phenylalkyl chlorides are often accompanied by rearrangements. The ease of formation of a six-membered ring (tetralin derivative) is much greater than that of a five-membered ring (indane derivative), based on entropy and strain factors. Khalaf and Roberts have performed stereochemical studies on cycloalkylation reactions to determine the effect of stereochemistry and steric factors in the formation of six-membered rings. 

This high-potential quinone is second in effectiveness to 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in the dehydrogenation of tetralin, acenaphthene, and dibenzyl in benzene at SO"." Kinetic studies are reported. The dehydrogenation of the 1,1-dimethyltetralin is attended with Wagner-Meerwein rearrangement ... 

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