Functionalized Aminocyclopropanes From Functionalized Organozinc Compounds and N,N-Dialkylcarboxamides
作者:Stefan Wiedemann、Ilan Marek、Armin de Meijere
DOI:10.1055/s-2002-31906
日期:——
Inter- as well as intramolecular competition experiments have been performed to demonstrate that N,N-dialkylcarboxamides react faster than tert-butyl esters with the titanium intermediates formed from ethylmagnesium bromide and methyltitanium triisopropoxide to selectively yield cyclopropylamines rather than cyclopropanols. Thus, functionalized organozinc reagents including a series with tert-butyl ester functionalities could be employed under newly developed conditions to transform N,N-dialkylformamides into chloroalkyl-substituted N,N-dialkylcyclopropylamines (55-67%) and tert-butyl (N,N-dialkylaminocyclopropyl)alkanoates (24-63% yield).
A New Versatile Reagent for the Synthesis of Cyclopropylamines Including 4-Azaspiro[2.n]alkanes and Bicyclo[n.1.0]alkylamines
作者:Vladimir Chaplinski、Harald Winsel、Markus Kordes、Armin de Meijere
DOI:10.1055/s-1997-17828
日期:——
The reaction of dialkylcarboxamides 1 with 1 equiv. of methyltriisopropyloxytitanium together with only 1.1 equiv. of a Grignard reagent gives cyclopropylamines 3 in better yields than the previously published method with 2 equiv. of Grignard reagent and 1 equiv. of Ti(OiPr)4. This new protocol can be applied to intramolecular reactions with in situ generation of the Grignard reagent from Ï-bromo-N,N-dimethylhexanamide and methyl Ï-bromohexanoate yielding the expected 1-dimetehylaminocyclo[4.1.0]hexane 15 and the corresponding alcohol 18. Cyclohexylmagnesium bromide or chloride transforms N,N-dibenzylformamide and ethyl acetate to 7-exo-N,N-dibenzylaminonorcarane and 7-exo-hydroxy-7-methylnorcarane. N-Methyl-â-caprolactam 25b and even the strained N-benzylpropiolactam 25a were converted to the spirocyclopropanated heterocycles 26a,b.
Unexpected titanium shifts during cyclopropanation of N,N-dibenzylformamide with ligand-exchanged titanium-alkadiene complexes
作者:Craig M. Williams、Vladimir Chaplinski、Peter R. Schreiner、Armin de Meijere
DOI:10.1016/s0040-4039(98)01665-7
日期:1998.10
A number of readily available dienes and a triene were applied to exchange the alkene ligand on the in situ generated titanium-alkene complexes which react with N,N-dialkylcarboxamides to give N,N-dialkylcyclopropylamines. The ligand-exchanged intermediates were found to give the most highly substituted alkenylcyclopropylamines (abnormal products) in good yields (47-64%), rather than the least substituted alkenylcyclopropylamine (expected products). This has been attributed to an unforeseen and unprecedented titanium migration along the ligand. (C) 1998 Elsevier Science Ltd. All rights reserved.
Mono- and Disubstituted N,N-Dialkylcyclopropylamines from Dialkylformamides via Ligand-Exchanged Titanium–Alkene Complexes Part 79 in the series “Cyclopropyl Building Blocks for Organic Synthesis”. For part 78 see: M. Gensini, I. Kozhushkov, S. Yufit, K. Howard, M. Es-Sayed, de Meijere, Eur. J. Org. Chem. 2002, 2499–2507; part 77: H. Nüske, S. Bräse, I. Kozhushkov, M. Noltemeyer, M. Es-Sayed, de Meijere, Chem. Eur. J. 2002, 8, 2350–2369.
作者:Armin de Meijere、Craig M. Williams、Alexandre Kourdioukov、Sergei V. Sviridov、Vladimir Chaplinski、Markus Kordes、Andrei I. Savchenko、Christian Stratmann、Mathias Noltemeyer
Dibenzylformamide was treated with cyclohexylmagnesium bromide in the presence of either titanium tetraisopropoxide or methyltitanium triisopropoxide and a variety of cyclic and acyclic alkenes and alkadienes to give new mono- and disubstituted as well as bicyclic dialkylcyclopropylamines (Tables 1-3) in yields ranging from 18 to 90 % (in most cases around 55 %). 3-Benzyl-6-(N,N-dibenzylamino)-3-azabicyclo[3
Easy access to various substituted 4-aminocyclopentenes by rearrangement of 2-ethenyl-substituted cyclopropylamines
作者:Craig M. Williams、Armin de Meijere
DOI:10.1039/a807012a
日期:——
A variety of 2-ethenyl-substituted cyclopropylamines upon flash vacuum pyrolysis or under silver nitrate catalysis cleanly undergo ring enlargement and afford high yields (up to 95%) of 4-aminocyclopent-1-enes, some of which have unprecedented substitution patterns.