1073-14-9Relevant academic research and scientific papers
Insertion reactions of silacyclopropanes: Evidence for a radical-based mechanism
Rotsides, Christina Z.,Woerpel
, p. 3132 - 3138 (2016)
Silacyclopropanes reacted rapidly and selectively with p-benzoquinones to provide oxasilacyclopentanes. Ring-expansion products were observed in the absence of a catalyst, elevated temperatures, or irradiation. As substitution was increased on the silacyclopropane ring, improved stereoselectivity was observed. In some cases, the regiochemistry was controlled depending on the extent of stabilization of the reactive intermediates involved. A radical clock experiment, along with stereochemical studies, confirmed that radical intermediates were involved in the ring-expansion reaction. The scope of this radical reaction was expanded to include dienones, aryl aldehydes, and electron-deficient enones in addition to benzoquinones. In the case of aryl aldehydes and electron-deficient enones, the radical reaction can be used to generate silylenes from silacyclopropanes.
Electrocatalytic dehalogenation of α-bromoketones in the presence of Cp2TiCl2
Nikitin,Gavrilova,Magdesieva
, p. 1013 - 1019 (2007)
Processes of direct and electrocatalytic (in the presence of electrochemically reduced Cp2TiCl2) reduction of three α-bromoketones containing the C(sp3)-Br or C(sp2)-Br bond, viz., 2-bromo-and 2,6-dibromo-4,4-dimethylcyclohexa-2,5-dien-1-ones and α-bromo-acetophenone, were studied by cyclic voltammetry and preparative electrolysis. In all cases, the dissociative electron transfer proceeds via the concerted mechanism. Preparative electrolysis of these α-bromoketones in the presence of Cp2TiCl2 affords the reductive debromination products in 40-80% yield at low cathodic potentials (-0.85 V vs. Ag/AgCl/KCl). In the case of 2,6-dibromo-4,4-dimethylcyclohexa-2,5-dien-1-one in the potentiostatic regime, only one bromine atom can be eliminated selectively.
Electrochemically induced transformation of 4-halomethyl-4-methylcyclohexa- 2,5-dien-1-ones into 3,4-dimethylphenol
Gavrilova,Moiseeva,Beloglazkina,Gavrilov,Zyk
, p. 264 - 268 (2009)
Electrochemical behavior of 4-halomethyl-4-methylcyclohexa-2,5-dien-1-ones and 2,6-dibromo-4,4-dimethylcyclohexa-2,5-dien-1-one was studied. Reductive dehalogenation of cyclohexa-2,5-dien-1-ones having a halogen atom at the neopentyl-like carbon atom give
Cross-conjugated compounds: microwave spectrum of 4,4-dimethyl-2,5-cyclohexadien-1-one
Hutter, Wolfgang,Bodenseh, Hans-Karl
, p. 151 - 158 (1993)
4,4-Dimethyl-2,5-cyclohexadien-1-one has been prepared by a three-step reaction from 4,4-dimethyl-2-cyclohexen-1-one.Microwave transitions of the cross-conjugated compound have been measured over extended regions from 11 to 40 GHz.The spectrum is a classical a-type spectrum of a near-prolate top with many interspersed lines presumably originating from excited vibrational states.No internal rotation splitting could be observed.We were able to assign 108 rotational transitions with J-quantum numbers up to 40.The least-squares fit showed a standard deviation of 30 kHz and yielded the three rotational constants, A = 3332.158(13) MHz, B = 1193.07386(52) MHz, C = 1082.21280(45) MHz, as well as all five quartic centrifugal distortion constants from Watson's A-reduction: ΔJ = 0.02149(73) kHz, ΔJK = 1.1008(16) kHz, ΔK = -68.42(32) kHz, δJ = 0.00332(16) kHz, δK = -2.7513(99) kHz (representation IR used).The dipole moment was determined from the Stark shift of the M-components of two transitions and was found to be 4.4522(83) D from 93 measurements.
Strong and Confined Acids Control Five Stereogenic Centers in Catalytic Asymmetric Diels–Alder Reactions of Cyclohexadienones with Cyclopentadiene
Bistoni, Giovanni,Das, Sayantani,De, Chandra Kanta,Ghosh, Santanu,Leutzsch, Markus,List, Benjamin,Neese, Frank,Yepes, Diana
supporting information, p. 12347 - 12351 (2020/03/23)
We describe a highly enantioselective Diels–Alder reaction of cross-conjugated cyclohexadienones with cyclopentadiene, in which five stereocenters are effectively controlled by a strongly acidic and confined imidodiphosphorimidate catalyst. Our approach provides tricyclic products in excellent stereoselectivity. We also report methods to convert the obtained products into useful intermediates and a computational study that aids in gaining deeper insight into the reaction mechanism and origin of stereoselectivity.
Lewis Acid Catalyzed Enantioselective Photochemical Rearrangements on the Singlet Potential Energy Surface
Leverenz, Malte,Merten, Christian,Dreuw, Andreas,Bach, Thorsten
supporting information, p. 20053 - 20057 (2019/12/30)
The oxadi-methane rearrangement of 2,4-cyclohexadienones to bicyclic ketones was found to proceed with high enantioselectivity (92-97% ee) in the presence of catalytic amounts of a chiral Lewis acid (15 examples, 52-80% yield). A notable feature of the transformation is the fact that it proceeds on the singlet hypersurface and that no triplet intermediates are involved. Rapid racemic background reactions were therefore avoided, and the catalyst loading could be kept low (10 mol %). Computational studies suggest that the enantioselectivity is determined within a Lewis acid bound singlet intermediate via a conical intersection. The utility of the method was demonstrated by a concise synthesis of the natural product trans-chrysanthemic acid.
Silver(I)-catalyzed ring-contractive rearrangement: A new entry to 5-alkylidene-2-cyclopentenones
Zhao, Liang,Wang, Jinlian,Zheng, Hongyan,Li, Yun,Yang, Ke,Cheng, Bin,Jin, Xiaojie,Yao, Xiaojun,Zhai, Hongbin
supporting information, p. 6378 - 6381 (2015/01/09)
A novel silver(I)-catalyzed ring-contractive rearrangement of 5-substituted 6-diazo-2-cyclohexenones has been developed, providing a new and efficient access to 5-alkylidene-2-cyclopentenones. The AgOTf-catalyzed reaction proceeds through metal-carbenoid formation followed by endocyclic allyl [1,2] migration with excellent stereoselectivity and broad substrate scope.
NMR-based molecular ruler for determining the depth of intercalants within the lipid bilayer. Part I. Discovering the guidelines
Cohen, Yael,Bodner, Efrat,Richman, Michal,Afri, Michal,Frimer, Aryeh A.
experimental part, p. 98 - 113 (2009/12/31)
The development of "molecular rulers" would allow one to quantitatively locate intercalants within the liposomal bilayer. To this end, we have attempted to correlate the 13C NMR chemical shift of a polarizable "reporter" carbon (e.g., carbonyl) of the intercalant-with the ET(30) polarity it experiences, and with its Angstrom distance from the interface. This requires families of molecules with the same two "reporter carbons" separated by a fixed distance, residing at various depths/polarities within the bilayer. The families studied included 4,4-dialkylcyclohexa-2,5-dienones 1, benzenediacetic esters 15, benzenedipropionic esters 17, 4-alkoxybenzaldehydes 19 and methyl 4-alkoxybenzoates 22. These compounds possessed the following characteristics: (1) a planar backbone; (2) polar/hydrophilic "head" groups; (3) modular hydrophobic tails; (4) large changes in the 13C NMR chemical shift (Δδ) of the reporter atoms with solvent polarity. These studies revealed a fifth requirement, namely: (5) the reporter carbons must not be strongly conjugated, lest it reflect the charge build-up at another site within the conjugated system.
4,4-Dimethylbicyclohexa-1(6),2-diene - A Highly Strained 1,3-Bridged Cyclopropene
Albers, Reinhard,Sander, Wolfram,Ottosson, Carl-Henrik,Cremer, Dieter
, p. 967 - 973 (2007/10/03)
The photochemical rearrangement of 4,4-dimethylcyclohexa-2,5-dienylidene (3) to 4,4-dimethylbicyclohexa-1(6),2-diene (5) was investigated by means of the matrix isolation technique.Carbene 3 was generated in argon matrices at 10 K by photolysis of
Competitive epoxidation and quinone formation in the dimethyldioxirane oxidation of diazoquinones as ambident nucleophiles
Adam, Waldemar,Hadjiarapoglou, Lazaros,Mielke, Karsten,Treiber, Alexander
, p. 5625 - 5628 (2007/10/02)
In addition to the expected dimethyldioxirane (DMD) oxidation of diazoquinones 1 to their quinones 2, the corresponding epoxy quinones 3 are formed directly and not as secondary overoxidation products of the quinones 2 since the latter are persistent towards DMD under these conditions; this novel oxidation is rationalized in terms of the ambident nucleophilic nature of the diazoquinones and corroborated by MO (AMI) calculations.
