Umlagerung von Allyl‐aryläthern und Allyl‐cyclohexadienonen mittels Bortrichlorid

Abstract

Ally1 aryl ethers which have no strongly electron attracting substitueuts undergo a charge-induced [3s, 3s] sigmatropic rearrangement in the prescence of 0.7 mole boron trichloride in chlorobenzene at low temperature, to give after hydrolysis the corresponding 0-ally1 phenols (Tables 1 and 2). The charge induction causes an increase in the reaction rate relative to the thermal Claisen rcarrangement of N 1O1O. With the exception of sllyl 3-methoxyphenyl ether (5). m-substituted allyl aryl ethers show similar behaviour (with respect to the composition of the product mixture) t o that observed in the thermal rearrangement (Table 3). The rearrangement of allyl aryl cthcrs wnth an alkyl group in the o-position, in the presencc of boron trichloride, yields a mixture of 0-and p-ally1 phenols, where more p-product is present than in the corresponding 1)

The Claisen rearrangement of 1,4-bis(m-methoxyphenoxy-)2-butyne

“…The presence of large quantities of chromenes (2) shortly after the start of the reaction indicates that the second step involves a rapid [1,5] hydrogen shift, to yield the w-vinylquinone methide 9, and subsequent electrocyclic ring closure. As an alternate possibility, 8 may undergo another Claisen rearrangement to a 2,3-diarylbutadiene (10) from which 3, 4, and the minor by-prod;ct 11 could be formed directly by two successive cyclizations (16).…”

Säurekatalysierte Dienon‐Phenol‐Umlagerungen von 6‐Propargyl‐6‐methyl‐cyclohexa‐2,4‐dien‐1‐onen; ladungskontrollierte, aromatische [1s, 2s]‐ und [3s, 4s]‐sigmatropische Reaktionen

“…1-Propargyl-7-methyl-2-0x0-I, 2-dihydvonaphthalin (16). Dieses o-Dienon wurde nach [4] synthetisiert. Ausgehend von 1,6 g (10 mmol) 1-Methyl-2-naphthol erhielt man 548 mg (27,9%) 16 als gelbliches 01, welches bei 100-105°/0,03 Torr destilliert wurde.…”

“…Arbeit [3] ; 6,12 (t, J1,,,, = 7,O Hz; H an C(1')); 4,85 (d,J,,,,,= 7,O Hz; 2H an C(3')); 2,25 (s; OCOCH, an C(1)); 2,19,2,08 und 2,02 (3s;CH,an C(2). C(4) und C (6) …”

Heteropoly Acid Encapsulated SBA‐15/TiO2 Nanocomposites and Their Unusual Performance in Acid‐Catalysed Organic Transformations

“…Very recently, a variety of Lewis acids, such as BF 3 ·AcOH, BCl 3 , Et 2 AlCl·TiCl 4 , and (iPrO) 2 TiCl 2 , have been employed to accelerate this rearrangement under much milder conditions. [47][48][49][50] However, these catalysts are associated with a number of disadvantages, including difficulty of separation from the reaction mixture, toxicity, and lower chemical and mechanical stability. These problems might be overcome by employing suitable highly acidic solid catalysts with high chemical and mechanical stability.…”