Kupfersalz‐katalysierte Homologisierung von Benzolderivaten mit Diazomethan zu Cycloheptatrien‐Derivaten

Abstract

Die Ringerweiterung von Benzol mit Diazomethan in Gegenwart von Kupfersalzen la& sich mit guten Ausbeuten auf substituierte Benzole unter Bildung von Cycloheptatrien-Derivaten anwenden. Der elektrophile Reaktionsmechanismus wird durch die aufgefundenen Isomerenverhaltnisse und durch Konkurrenzversuche gestiitzt.

Seven-membered conjugated carbo- and heterocyclic compounds and their homoconjugated analogs and metal complexes. Synthesis, biosynthesis, structure, and reactivity

“…Cycloheptatriene (78) was obtained by sodium borohydride reduction of 79.58a By this method, methylene Insertion in the aromatic ring of a variety of substituted benzenes has also been achieved. 59 This method583 is definitely superior to the photochemical one58b which gives large percentages of products of methylene Insertion into either aliphatic or aromatic C-H bonds.…”

Molybdenum Complexes with Sterically Demanding Cycloheptatrienyl Ligands

“…Triphenylcarbenium tetrafluoroborate, N -methyl- N -nitrosourea, [(η 6 - p- xylene)Mo(CO) 3 ], (C 7 H 6 CMe 3 )BF 4 ( 3c ), and (C 7 H 6 SiMe 3 )BF 4 ( 3d ) were prepared according to published procedures. In principle, the preparation of salts containing the 1,3,5-tri- tert -butyltropylium and the 1,3,5-triisopropyltropylium ions had been reported, 9b, and the improved protocol for the syntheses of 3a and 3b described here is based on a recipe provided by T. Kitagawa (Kyoto University).…”

“…The tropylium salts 3a and 3b can be prepared from the 1,3,5-substituted benzene derivatives 1a and 1b by CuBr-catalyzed ring-expansion with diazomethane 9b, followed by hydride abstraction from the resulting cycloheptatrienes 2a and 2b using triphenylcarbenium tetrafluoroborate, (Ph 3 C)BF 4 . The conversion of 1 into 2 generally proceeds in only modest yield (approximately 30%).…”

Cyclopropanation of Some Alkaloids

“…The formation of compound 4 occurs with insertion of a methylene group into the aromatic ring. The reaction is known in the literature and was mainly investigated in relatively simple aromatics to prepare tropylium salts with different substituents [33][34][35][36]. (The formation of compound 5 can be explained with an oxidative ring opening of 1; N-formylation reaction with diazomethane is known in the literature [37].…”

“…(The formation of compound 5 can be explained with an oxidative ring opening of 1; N-formylation reaction with diazomethane is known in the literature [37]. ) According to the literature [33] the Rh/C catalyst gives the best yields in these types of reaction and in some cases copper(I) halogenides, copper(I) chloride [34] and copper(I) bromide [35,36] were also effective. Using Rh/C catalyst no reaction was observed between 1 and diazomethane.…”