- Intermolecular Allene Functionalization by Silver-Nitrene Catalysis
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Under silver catalysis conditions, using [Tp*,BrAg]2 as the catalyst precursor, allenes react with PhI═NTs in the first example of efficient metal-mediated intermolecular nitrene transfer to such substrates. The nature of the substituent at the allene seems crucial for the reaction outcome since arylallenes are converted into azetidine derivatives, whereas methylene aziridines are the products resulting from alkylallenes. Mechanistic studies allow proposing that azetidines are formed through unstable cyclopropylimine intermediates, which further incorporate a second nitrene group, both processes being silver-mediated. Methylene aziridines from alkylallenes derive from catalytic nitrene addition to the allene double bonds. Both routes have resulted to be productive for further synthetic transformations affording aminocyclopropanes.
- Rodríguez, Manuel R.,Besora, María,Molina, Francisco,Maseras, Feliu,Díaz-Requejo, M. Mar,Pérez, Pedro J.
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supporting information
p. 13062 - 13071
(2020/09/01)
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- Stereoselective Desymmetrization of gem-Diborylalkanes by “Trifluorination”
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An efficient and general method for the chemoselective synthesis of unsymmetrical gem-diborylalkanes is reported. This method is based on a late-stage desymmetrization through nucleophilic “trifluorination”, providing chiral gem-diborylalkanes bearing a trifluoroborate group. The reaction offers a highly modular and diastereoselective approach towards the synthesis of gem-diborylcyclopropanes. The utility of the gem-diborylalkane building blocks was demonstrated by selective post-functionalization of the trifluoroborate group. These functionalizations include inter- and intra- Pd-catalyzed Suzuki–Miyaura coupling reactions.
- Kumar, Nivesh,Reddy, Reddy Rajasekhar,Masarwa, Ahmad
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supporting information
p. 8008 - 8012
(2019/05/28)
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- A convenient access to allylic triflones with allenes and triflyl chloride in the presence of (EtO)2P(O)H
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A simple method for the preparation of allylic triflones from allenes and triflyl chloride in the presence of (EtO)2P(O)H has been developed. The features of this reaction are catalyst-free and simple starting substrates. This method tolerates diverse functional groups and substituted allylic triflones are obtained in moderate to good yields.
- Ni, Jixiang,Jiang, Yong,An, Zhenyu,Lan, Jingfeng,Yan, Rulong
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supporting information
p. 7343 - 7345
(2019/06/27)
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- Highly selective cobalt-mediated [6 + 2] cycloaddition of cycloheptatriene and allenes
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[6 + 2] Cycloadditions between cycloheptatrienes with allenes have been investigated. Cobalt salts were found to promote this transformation efficiently. Moreover, this reaction was found to be highly selective since only one regioisomer was obtained with an excellent E/Z-selectivity.
- Clavier, Herve,Jeune, Karel Le,Riggi, Innocenzo De,Tenaglia, Alphonse,Buono, Gerard
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supporting information; experimental part
p. 308 - 311
(2011/04/15)
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- Can relief of ring-strain in a cyclopropylmethyllithium drive the Brook rearrangement?
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α-Cyclopropyl-α-trialkylsilyl alkoxides were formed either by addition of cyclopropyllithiums to acylsilanes or by addition of organolithiums to a cyclopropylformylsilane. [1,2]-Brook rearrangement led to α-silyloxy organolithiums which on warming underwent cyclopropane ring opening and [1,5]-retro-Brook rearrangement to yield γ-silyl ketones. Despite the favourability of the cyclopropane ring opening, the Brook rearrangement still required the presence of an anion stabilising group to proceed. β-Silylketones were similarly formed by Brook-retro-Brook rearrangement on warming acylsilanes with a vinyllithium.
- Clayden, Jonathan,Watson, David W.,Chambers, Mark
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p. 3195 - 3203
(2007/10/03)
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- Kupfer(II)-chlorid-katalysierte 'Carben-Dimerisierung' von 1-Halogeno-1-lithiocyclopropanen: Ein einfacher Zugang zu Bi(cyclopropylidenen)
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A series of 13 bi(cyclopropylidenes) 11 are prepared in a simple one-pot reaction by halogeno-lithio exchange between 1,1-dibromocyclopropanes 1a-n and BuLi, in most cases at -95 deg C, to give 1-bromo-1-lithiocyclopropanes 2a-n, followed by treatment with CuCl2 at low temperature and a simple workup at room temperature (Scheme 3c and Table 1).The yields of bi(cyclopropylidenes) 11 strongly depend on reaction parameters, as explicitly shown for the conversion 1f->-> 11f (Tables 2-8).Mixed couplings between two different carbenoids are possible (Scheme 4), while diastereoselectivity of the active transition-metal complex seems to be low.The structures of bi(cyclopropylidenes) 11 are confirmed by spectroscopic data as well as by X-ray analysis of an isolated crystalline diastereomer of 11k (Fig. 1).
- Loosli, Thomas,Borer, Markus,Kulakowska, Iga,Minger, Andrea,Neuenschwander, Markus,Engel, Peter
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p. 1144 - 1165
(2007/10/02)
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- A simple synthesis of gem-bromochlorocyclopropanes via phase-transfer catalysis
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Substituted 1-bromo-1-chlorocyclopropanes 2 were synthesized from dibromomethane, phenyltrichloromethane trichloride and alkenes 1 in the presence of 60% aqueous potassium hydroxide and tetrabutylammonium hydrogen sulfate as a catalyst (PTC system), in good yields.
- Balcerzak,Jonczyk
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p. 857 - 858
(2007/10/02)
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