Thallium trinitrate-mediated ring contraction of 1,2-dihydronaphthalenes: the effect of electron-donating and electron-withdrawing groups

Abstract

A oxidação de uma série de 1,2-diidronaftalenos, substituídos no anel aromático, foi investigada com trinitrato de tálio (TTN) em metanol ou em trimetilortoformiato (TMOF) como solvente. Em todos os casos, indanos foram formados, embora o rendimento tenha variado de excelente a baixo, dependendo da estrutura do substrato. A presença de um grupo doador de elétrons no substrato favorece o rearranjo, enquanto que uma quantidade significativa de derivados glicólicos, bem como naftalenos, foi obtida na oxidação de 1,2-diidronaftalenos com um grupo retirador de elétrons, tais como Br e NO 2 . Mecanismos para a formação de cada um destes produtos foram propostos.The oxidation of a series of 1,2-dihydronaphthalenes substituted in the aromatic ring was investigated with thallium trinitrate (TTN) in methanol or in trimethylorthoformate (TMOF) as solvent. In all cases, indans are produced, although the yield varied from excellent to poor, depending on the structure of the substrate. The presence of an electron-donating group in the substrate favors the rearrangement, whereas significant amounts of glycolic derivatives, as well as naphthalenes, were obtained in the oxidation of 1,2-dihydronaphthalenes bearing electron-withdrawing groups, such as Br and NO 2 . Mechanisms for the formation of each of these products are proposed.ring contraction reaction. The present article describes a detailed study of the TTN-mediated oxidation of 1,2dihydronaphthalenes bearing different groups in the aromatic ring (Me, OMe, OH, NH 2 , NHAc, Br and NO 2 ), better defining the scope of this reaction, which will facilitate future applications. In addition, a more clear picture of the mechanism of the thallium(III)-mediated oxidation of olefins could be drawn based on the new results.

Seven-Membered Rings through Metal-Free Rearrangement Mediated by Hypervalent Iodine

“…A substituent in the aromatic ring can alter the migratory aptitude of the migrating carbon, which may influence the yield of the rearrangement product. For example, a correlation between yield of the product and migratory aptitude was noted by us in Tl(III)-mediated ring contraction of 1,2-di-hydronaphthalenes [43]. Thus, we investigated the ring expansion of 3 with different groups in the aromatic ring.…”

Indatraline: Synthesis and Effect on the Motor Activity of Wistar Rats

“…When the dehydration was performed with H 3 PO 4 , the 1,2-dihydronaphthalene was isolated in good yield only on a small scale. Using more than 1 mmol of starting material 6 , the formation of a complex mixture was observed [ 30 ].…”

“…The oxidation of 1,2-dihydronaphthalene 5 with iodine(III) [ 20 , 22 , 31 , 32 , 33 , 34 ] or with thallium(III) [ 30 , 31 , 33 , 35 , 36 , 37 , 38 , 39 , 40 ] in MeOH furnished the indane 4 , the naphthalene 7 and the addition product 8 , depending on the reaction conditions ( Table 1 ). With 0.9 equiv.…”

Rearrangement of beta,gamma-unsaturated esters with thallium trinitrate: synthesis of indans bearing a beta-keto ester moiety

“…2,3 Our research group has investigated approaches to obtain indans from 1,2-dihydronaphthalenes, using a thallium(III)-promoted ring contraction reaction. [4][5][6][7][8][9] During these studies, we found that a side chain at the double bond has a strong influence in the reaction pathway. 5 The treatment of 1,2-dihydronaphthalenes bearing a β,γ-unsaturated carboxylic acid unit, such as 1, with thallium triacetate (TTA) gave a mixture of the isomeric allylic acetates 2 and 3, which are produced through an oxidative decarboxylation process (Scheme 1).…”

“…4,6 The homoallylic alcohols 7 were efficiently obtained in three steps from 1-tetralones, through the β,γ-unsaturated esters 6. We then realized that these esters would also be interesting substrates for thallium(III)-promoted ring contraction reactions, because the indans products of this transformation (9), would bear a β-keto ester unit, which is a valuable moiety for further functionalization 11 (Scheme 3).…”