- Thermal Isomerizations of 1,1-Dimethyl-2,2-d2-cyclopropane
-
The gas-phase thermal isomerization of 1,1-dimethylcyclopropane at 420 °C gives 3-methyl-1-butene and 2-methyl-2-butene. The mixture of products formed from 1, l-dimethyl-2,2-d2-cyclopropane is consistent with conventional rationales; neither tert-butylcarbene nor isobutylcarbene is involved as a mechanistically significant intermediate. Both kinetic and deuterium labeling evidence suggests that heterogeneous wall-catalyzed processes afford secondary products, including 2-methyl-1-butene.
- Baldwin, John E.,Shukla, Rajesh
-
-
Read Online
- Tandem Hydroalumination/Cu-Catalyzed Asymmetric Vinyl Metalation as a New Access to Enantioenriched Vinylcyclopropane Derivatives
-
Herein, we report the first enantio- and diastereoselective addition of stereodefined vinyl organometallic reagents to cyclopropenes. The operationally simple tandem hydroalumination and copper-catalyzed vinylmetalation allows for the unique access of a diverse set of enantioenriched vinylcyclopropane derivatives.
- Müller, Daniel S.,Werner, Veronika,Akyol, Sema,Schmalz, Hans-Günther,Marek, Ilan
-
supporting information
p. 3970 - 3973
(2017/08/14)
-
- An efficient synthesis of cyclopropyl silyl ketones
-
The reaction of silylcyclopropyl bromides with dichloromethyl methyl ether in the presence of n-butyllithium is investigated. Under basic reaction conditions, the corresponding cyclopropylidene derivatives are exclusively obtained. The resulting cyclopropylidene compounds are subjected to protonolysis or trapping with electrophiles in a one-pot to give the cyclopropyl silyl ketone derivatives in good yields. Acidic treatment of derived cyclopropyl silyl ketone allows isomerization to give the thermodynamically favorable trans form exclusively.
- Honda, Mitsunori,Nakae, Kenta,Nishizawa, Toshiaki,Suda, Mitsuhiro,Kunimoto, Ko-Ki,Segi, Masahito
-
body text
p. 9500 - 9508
(2012/01/02)
-
- Hydrodehalogenation of 1,1-dibromocyclopropanes by Grignard reagents promoted by titanium compounds
-
1,1-Dibromocyclopropanes are converted into the corresponding monobromocyclopropanes (as mixtures of stereoisomers where appropriate) by reaction with 1.0-1.3 mol equiv. of ethylmagnesium bromide and 2-10 mol% titanium isopropoxide for 90%). With ethylmagnesium bromide, the reaction occurs very slowly in the absence of catalyst; with methylmagnesium bromide, the reaction does occur in the absence of catalyst, but is only slightly promoted in the presence of titanium isopropoxide. Reactions with a number of other Grignard reagents are also discussed. In the case of phenethylmagnesium bromide, the major product containing the phenethyl-group is ethylbenzene, together with small amounts of styrene and ethyl 4-phenyl-2-butyl ether, a product of trapping of the solvent, ether. In other cases, relatively large amounts of a diether, formally derived by hydrogen ion adjacent to the ether oxygen followed by dimerisation, are isolated. No products were identified incorporating the cyclopropane and either the Grignard alkyl group or the solvent. Labelling studies indicate that the hydrogen introduced into the cyclopropane is not derived from either the α- or β-positions of the Grignard reagent. When the reduction is carried out with phenethylmagnesium bromide in d8-tetrahydrofuran both monobromides contain deuterium.
- Dulayymi, Juma'a R. Al,Baird, Mark S.,Bolesov, Ivan G.,Nizovtsev, Alexey V.,Tverezovsky, Viacheslav V.
-
p. 1603 - 1618
(2007/10/03)
-
- New complexes of platinum(0) with cyclopropenes
-
New cyciopropene complexes of platinum have been synthesised with a variety of bulky substituents on all positions of the cyciopropene ring. Two of these novel complexes, [Pt(3,3-Ph3C3H2)(PPh3)2] and [Pt(1,2-Ph2C3H2)(PPh3)2J, have been structurally characterised by X-ray analysis. Both contain a cyciopropene ring which has remained intact upon complexation. The bond lengths within the complexes are remarkably independent of the substituents. The structural characteristics and the 31P NMR spectra of these complexes are discussed in detail.
- Hughes, David L.,Leigh, G. Jeffery,McMahon, C. Niamh
-
p. 1301 - 1307
(2007/10/03)
-
- SELECTIVITY IN THE REACTIONS OF 3,3-DISUBSTITUTED CYCLOPROPENES WITH NITRILE OXIDES
-
The reactions of 3-R-3-R'-disubstituted cyclopropenes with nitrile oxides lead to the formation of 4,6,6-trisubstituted 2-oxa-3-azabicyclohex-3-enes, which can be isolated with high yields.Substituents at C3 of the cyclopropane ring (phe
- Bolesov, I. G.,Ignatchenko, A. V.,Bovin, N. V.,Prudchenko, I. A.,Surmina, L. S.,et al.
-
-
- Synthesis and Structure of Adamantyl-Substituted Methyleneaziridines
-
The thermolysis of the 1,1-dibromocyclopropanes 3b, c in the presence of primary amines produced the 3,3-disubstituted N-alkyl(2-bromo-2-propen)amines 2b, c.These as well as 2a afforded the 1-alkyl-2-alkylideneaziridines 4 on 1,3-dehydrobromination with sodium amide in liquid ammonia.The isopropylideneaziridine 4b crystallizes monoclinically as a racemate in the space group P21/n with four molecules per cell.The angle between the plane of the three-membered ring and the 1-adamantyl nitrogen bond is 55.4 deg.Some structural parameters of 4b are discussed.
- Quast, Helmut,Jakob, Roland,Peters, Karl,Peters, Eva-Maria,Schnering, Hans Georg von
-
p. 840 - 849
(2007/10/02)
-
- Reaktion von 1,2,4,5-Tetrazin-3,6-dicarbonsaeure-dimethylester mit 3,3-Dimethylcyclopropen: Unerwartete Bildung eines -Addukts
-
Reaction of tetrazine 1 with 3,3-dimethylcyclopropene (2) at lower temperature leads to the expected products 3 and 4; in addition a -adduct 7 is isolated at higher temperature (>80 deg C).Its structure was ascertained by spectroscopic data and X-ray structure analysis.
- Huber, Franz-Xaver,Sauer, Juergen,McDonald, Walter S.,Noeth, Heinrich
-
p. 444 - 451
(2007/10/02)
-
- EXPERIMENTAL EVIDENCE FOR A CORRELATION BETWEEN ISOSELECTIVE AND ISOKINETIC TEMPERATURES
-
From isokinetic temperatures β (Figures I and II) and activation enthalpies (Table I) an isoselective temperature of 368 K is calculated for cycloaddition reactions of dihalocarbenes with alkenes.This is in excellent accord with the experimental value of 360 +/- 10 K.
- Giese, Bernd,Lee, Woo-Bung
-
p. 3561 - 3564
(2007/10/02)
-
- Selectivity of Dihalocarbenes in Cycloaddition Reactions
-
Dihalocarbenes 1a-e yield in the 2-methyl-2-butene/2-methylpropene competition system the cyclopropanes 2a-e and 3a-e.Whereas selectivity increases at 293 K in the sequence CBr2 CClBr CCl2 CFCl CF2, at 393 K the order of carbene selectivity is reversed: CF2 CFCl CCl2 CClBr CBr2 (Table 1).At 360 K (isoselective temperature) the carbenes 1a-e react with equal selectivity.The reason for this is that activation enthalpies and activation entropies are changed in the same direction with variation of carbene substituents from fluorine to bromine (Table 2).Thereby the selectivities of CClBr and CBr2 increase with increasing temperature (Figure 2). - Above and below 360 K the order of the slopes of carbenes 1a-e are reversed in the Skell-Moss diagram (Figure 3).
- Giese, Bernd,Lee, Woo-Bung,Meister, Juergen
-
p. 725 - 735
(2007/10/02)
-