- Determination of the photolytic decomposition pathways of benzylchlorodiazirine by C60 probe technique
-
By employing C60 as a chemical probe, the photolysis of benzylchlorodiazirine has been proposed to form carbene and the rearranged products via the excited state.
- Ishitsuka, Midori O.,Enoki, Haruka,Nikawa, Hidefumi,Wakahara, Takatsugu,Tsuchiya, Takahiro,Akasaka, Takeshi,Liu, Michael T.H.
-
-
Read Online
- Kinetics of the 1,5-Dipolar Cyclization of 2-Vinylpyridinium Ylides to Indolizines. Determination of Rate Parameters by Laser Flash Photolysis
-
Nanosecond laser flash photolysis (λ = 355 nm) of an aqueous solution of 3-chloro-3-p-chlorophenyldiazirine in isooctane produces a transient absorption at 310 nm due to the formation of the carbene. In the presence of 2-vinylpyridine, a second transient with a broad absorption band peaking at 520 nm grows in. This absorption is attributed to 2-vinylpyridinium ylide. The ylide decays with a lifetime equal to 33 μs at 25 deg C independent of the concentration of 2-vinylpyridine. As the ylide decays, there is a concomitant growth of an absorption at 330 nm, attributed to the formation of indolizine. The activation parameters for the 1,5-dipolar cyclization of the ylide to indolizine were determined; Ea = 12.1 kcal mol-1 and log A = 13.4.
- Liu, Michael T. H.,Romashin, Yuri N.,Bonneau, Roland
-
-
Read Online
- Benzylchlorocarbene: Origins of Arrhenius Curvature in the Kinetics of the 1,2-H Shift Rearrangement
-
Benzylchlorocarbene (1, BCC) was generated photochemically from benzylchlorodiazirine (2) in isooctane, methylcyclohexane (MCH), and tetrachloroethane (TCE) at temperatures from ~30 to -75°C. At -70°C in isooctane, the identified products included Z/E-β-chlorostyrenes 4 (46.6%), α-chlorostyrene 5 (2.4%), l,1-dichloro-2-phenylethane 6 (1.9%), a BCC-isooctane insertion product 8 (5.5%), carbene dimers 9 (3.8%), and azine 3 (30%). The significant incursion of intermolecular products 3, 8, and 9 implies that laser flash photolytic (LFP) kinetic data for the decay of BCC obtained at low temperature is biased and should not be employed in Arrhenius analyses. Accordingly, previously obtained curved Arrhenius correlations for BCC do not necessarily implicate , quantum mechanical tunneling (QMT) in the 1,2-H shift rearrangement of BCC to 4. Similarly in MCH, where BCC affords a solvent insertion product in ~44-53% yield, the curved Arrhenius correlation (Figure 1) cannot be readily interpreted. In polar solvents such as TCE, clean H-shift reactions of BCC are obtained even at -71°C; an Arrhenius correlation of LFP kinetic data is linear from 3 to -71°C (Figure 2), affording Ea = 3.2 kcal mol-1 and log A = 10.0 s-1. Therefore, QMT does not appear to play a major role in the 1,2-H shift rearrangement of BCC at ambient or near ambient temperature in solution.
- Merrer, Dina C.,Moss, Robert A.,Liu, Michael T.H.,Banks,Ingold, Keith U.
-
-
Read Online
- Energy Barrier for 1,2-Hydrogen Migration in Benzylchlorocarbene
-
The intermolecular-intramolecular rate constants derived from the thermolysis and photolysis of 3-chloro-3-benzyldiazirine in tetramethylene gave an excellent Arrhenius plot; an activation energy of 6.4 kcal mol-1 (26.8 kJ mol-1) was obtained for the 1,2-H migration in benzylchlorocarbene.
- Liu, Michael T. H.
-
-
Read Online
- Visible light-mediated metal-free double bond deuteration of substituted phenylalkenes
-
Various bromophenylalkenes were reductively photodebrominated by using 1,3-dimethyl-2-phenyl-1H-benzo-[d]imidazoline (DMBI) and 9,10-dicyanoanthracene. With deuterated DMBI analogs (the most effective was DMBI-d11), satisfactory to excellent isotopic yields were obtained. DMBI-d11 could also be regenerated from the reaction mixtures with a recovery rate of up to 50%. The combination of the photodebromination reaction with conventional methods for bromoalkene synthesis enables sequential monodeuteration of a double bond without the necessity of a metal catalyst. This journal is
- Iakovenko, Roman,Hlavá?, Jan
-
supporting information
p. 440 - 446
(2021/01/28)
-
- Rhodium-Catalyzed Deoxygenation and Borylation of Ketones: A Combined Experimental and Theoretical Investigation
-
The rhodium-catalyzed deoxygenation and borylation of ketones with B2pin2 have been developed, leading to efficient formation of alkenes, vinylboronates, and vinyldiboronates. These reactions feature mild reaction conditions, a broad substrate scope, and excellent functional-group compatibility. Mechanistic studies support that the ketones initially undergo a Rh-catalyzed deoxygenation to give alkenes via boron enolate intermediates, and the subsequent Rh-catalyzed dehydrogenative borylation of alkenes leads to the formation of vinylboronates and diboration products, which is also supported by density functional theory calculations.
- Tao, Lei,Guo, Xueying,Li, Jie,Li, Ruoling,Lin, Zhenyang,Zhao, Wanxiang
-
p. 18118 - 18127
(2020/11/26)
-
- Shelf-Stable (E)- A nd (Z)-Vinyl-λ3-chlorane: A Stereospecific Hyper-vinylating Agent
-
We report the first stereoselective synthesis of stable (E)- A nd (Z)-β-chlorovinyl-λ3-chlorane via direct mesitylation of 1,2-dichloroethylene with mesityldiazonium tetrakis(pentafluorophenyl)borate under mild reaction conditions. The structure of the (E)-vinyl-λ3-chlorane was established by single-crystal X-ray analysis. Because of the enormously high leaving group ability of the aryl-λ3-chloranyl group, vinyl-λ3-chloranes undergo not only SNVσ-type reaction with extremely weak nucleophiles such as perfluoroalkanesulfonate, iodobenzene, and aromatic hydrocarbons but also coupling with phenylcopper(I) species.
- Kanazawa, Junichiro,Miyamoto, Kazunori,Takagi, Taisei,Uchiyama, Masanobu,Watanabe, Yuichiro
-
supporting information
p. 3469 - 3473
(2020/04/30)
-
- AgSbF6-Catalyzed: Anti -Markovnikov hydroboration of terminal alkynes
-
AgSbF6-Catalyzed anti-Markovnikov addition of pinacolborane (HBpin) to terminal alkynes to produce the E-vinylboronates is reported. This efficient methodology is scalable, compatible with sterically and electronically diverse alkynes, and works at room temperature under solvent-free condition. The utility of this method is demonstrated in the facile synthesis of the clinically important (E)-2,4,3′,5′-tetramethoxystilbene.
- Mamidala, Ramesh,Pandey, Vipin K.,Rit, Arnab
-
p. 989 - 992
(2019/01/23)
-
- Iron-Catalyzed Cross-Coupling of Alkynyl and Styrenyl Chlorides with Alkyl Grignard Reagents in Batch and Flow
-
Transition-metal-catalyzed cross-coupling chemistry can be regarded as one of the most powerful protocols to construct carbon–carbon bonds. While the field is still dominated by palladium catalysis, there is an increasing interest to develop protocols that utilize cheaper and more sustainable metal sources. Herein, we report a selective, practical, and fast iron-based cross-coupling reaction that enables the formation of Csp?Csp3 and Csp2?Csp3 bonds. In a telescoped flow process, the reaction can be combined with the Grignard reagent synthesis. Moreover, flow allows the use of a supporting ligand to be avoided without eroding the reaction selectivity.
- Deng, Yuchao,Wei, Xiao-Jing,Wang, Xiao,Sun, Yuhan,No?l, Timothy
-
supporting information
p. 14532 - 14535
(2019/11/21)
-
- Continuous Flow Chlorination of Alkenyl Iodides Promoted by Copper Tubing
-
A simple continuous flow synthesis of alkenyl chlorides from the corresponding readily available alkenyl iodides in copper reactor tubing is described. A variety of alkenyl chlorides were obtained in good to excellent yields with full retention of the dou
- Nitelet, Antoine,Kairouz, Vanessa,Lebel, Hélène,Charette, André B.,Evano, Gwilherm
-
p. 251 - 257
(2019/01/04)
-
- Reaction of Styrene with Chlorine Dioxide
-
Reaction of styrene with chlorine dioxide under various conditions selectively produces 1-phenyl- 2-chloroethanone, with 1-phenyl-2-chloroethanol, 2-hydroxy-1-phenylethanone, (1,2-dichloroethyl)benzene, (2-chloro-1-phenyl)ethene, and (1,2,2-trichloroethyl
- Loginova,Chukicheva, I. Yu.,Kuchin
-
p. 825 - 828
(2018/06/14)
-
- Development of a general copper-catalyzed vinylic Finkelstein reaction—application to the synthesis of the C1–C9 fragment of laingolide B
-
An efficient and broadly applicable procedure for the copper-catalyzed vinylic Finkelstein reaction is reported. Using a simple, readily available and cheap catalytic system, a broad range of alkenyl iodides and bromides can be smoothly converted to their lower homologues with high yields and full retention of the double bond geometry. Key features of this vinylic Finkelstein reaction are its broad applicability, enabling the conversion of readily available alkenyl iodides to their less available brominated and chlorinated counterparts, and the mild reaction conditions compatible with a range of highly functionalized substrates. The potential of this vinylic halogen exchange reaction in total synthesis and medicinal chemistry was demonstrated by its successful use for the synthesis of the C1–C9 fragment of laingolide B and for the late-stage modification of drug-like molecules. The extension of this halogen exchange to the acetylenic and allenic Finkelstein reactions is also reported.
- Nitelet, Antoine,Jouvin, Kévin,Evano, Gwilherm
-
p. 5972 - 5987
(2016/09/16)
-
- A General Copper-Catalyzed Vinylic Halogen Exchange Reaction
-
An efficient and general system for the halogen exchange reaction in alkenyl halides has been developed. Upon reaction with catalytic amounts of copper iodide and trans-N,N′-dimethylcyclohexane-1,2-diamine in the presence of tetramethylammonium chloride or bromide, a wide range of easily accessible alkenyl iodides can be smoothly transformed to their far less available chlorinated and brominated derivatives in excellent yields and with full retention of the double bond geometry. This reaction also enables the chlorination of bromoalkenes and could be extended to the use of gem-dibromoalkenes.
- Nitelet, Antoine,Evano, Gwilherm
-
supporting information
p. 1904 - 1907
(2016/05/19)
-
- A green hunsdiecker reaction of cinnamic acids
-
Tribromo- and trichloroisocyanuric acids react with cinnamic acids in NaOH/H2O/Et2O at room temperature to produce (E)-2-halostyrenes regioselectively in 25-95percent yield. Mechanism studies using Hammett correlations and DFT (density functional theory) calculations have shown that this reaction has as rate determining step the electrophilic addition of chlorine atom to the double bond.
- Sodre?, Leonardo R.,Esteves, Pierre M.,De Mattos, Marcio C. S.
-
p. 212 - 218
(2013/05/08)
-
- Rhodium-catalyzed cross-coupling of alkenyl halides with arylboron compounds
-
The rhodium(I)-catalyzed reaction between arylboronic esters and excess 1,2-dichloroethene selectively afforded (2-chlorovinyl)arenes. Double arylation yielding 1,2-diarylethenes was observed when 1,2-dibromoethene was reacted with 2.5 equivalents of aryl
- Matsuda, Takanori,Suzuki, Kentaro,Miura, Norio
-
supporting information
p. 3396 - 3400
(2013/12/04)
-
- Synthesis of 2- and 2,3-substituted Pyrazolo[1,5- a ]pyridines: Scope and mechanistic considerations of a domino direct alkynylation and cyclization of n -iminopyridinium ylides using alkenyl bromides, alkenyl iodides, and alkynes
-
Direct functionalization and tandem processes have both received considerable recent interest due to their cost and time efficiency. Herein we report the synthesis of difficult to obtain 2-substituted pyrazolo[1,5-a] pyridines through a tandem palladium-catalyzed/silver-mediated elimination/direct functionalization/cyclization reaction involving N-benzoyliminopyridinium ylides. As such, these biologically important molecules are prepared in an efficient, high-yielding manner, only requiring a two-step sequence from pyridine. Aryl-substituted alkenyl bromides and iodides are effective ylide coupling partners. Mechanistic studies led to the use of terminal alkynes, which extended the scope of the reaction to include alkyl substitution on the unsaturated reactive site. The optimization, scope, and mechanistic considerations of the process are discussed.
- Mousseau, James J.,Bull, James A.,Ladd, Carolyn L.,Fortier, Angelique,Sustac Roman, Daniela,Charette, Andre B.
-
experimental part
p. 8243 - 8261
(2012/01/03)
-
- Metal-free chlorodeboronation of organotrifluoroborates
-
A mild and metal-free method for the chlorodeboronation of organotrifluoroborates using trichloroisocyanuric acid (TCICA) was developed. Aryl-, heteroaryl-, alkenyl-, alkynyl-, and alkyltrifluoroborates were converted into the corresponding chlorinated products in good yields. This method proved to be tolerant of a broad range of functional groups.
- Molander, Gary A.,Cavalcanti, Livia N.
-
experimental part
p. 7195 - 7203
(2011/10/13)
-
- Bis- N -heterocyclic carbene palladium(IV) tetrachloride complexes: Synthesis, reactivity, and mechanisms of direct chlorinations and oxidations of organic substrates
-
This Article describes the preparation and isolation of novel octahedral CH2-bridged bis-(N-heterocyclic carbene)palladium(IV) tetrachlorides of the general formula LPdIVCl4 [L = (NHC)CH 2(NHC)] from LPdIICl2 and Cl2. In intermolecular, nonchelation-controlled transformations LPdIVCl 4 reacted with alkenes and alkynes to 1,2-dichlorination adducts. Aromatic, benzylic, and aliphatic C-H bonds were converted into C-Cl bonds. Detailed mechanistic investigations in the dichlorinations of alkenes were conducted on the 18VE PdIV complex. Positive solvent effects as well as kinetic measurements probing the impact of cyclohexene and chloride concentrations on the rate of alkene chlorination support a PdIV-Cl ionization in the first step. Product stereochemistry and product distributions from various alkenes also support Cl+-transfer from the pentacoordinated PdIV-intermediate LPdIVCl 3+ to olefins. 1-Hexene/3-hexene competition experiments rule out both the formation of π-complexes along the reaction coordinate as well as in situ generated Cl2 from a reductive elimination process. Instead, a ligand-mediated direct Cl+-transfer from LPd IVCl3+ to the π-system is likely to occur. Similarly, C-H bond chlorinations proceed via an electrophilic process with in situ formed LPdIVCl3+. The presence of a large excess of added Cl- slows cyclohexene chlorination while the presence of stoichiometric amounts of chloride accelerates both PdIV-Cl ionization and Cl+-transfer from LPdIVCl3 +. 1H NMR titrations, T1 relaxation time measurements, binding isotherms, and Job plot analysis point to the formation of a trifurcated Cl-...H-C bond in the NHC-ligand periphery as a supramolecular cause for the accelerated chemical events involving the metal center.
- McCall, A. Scott,Wang, Hongwang,Desper, John M.,Kraft, Stefan
-
supporting information; experimental part
p. 1832 - 1848
(2011/04/15)
-
- Synthesis, structure and reactivity of organogold compounds of relevance to homogeneous gold catalysis
-
Organogold(I) phosphane complexes were prepared, their structure was investigated and their reactivity in reactions with Michael acceptors, sources of electrophilic halogens and protons were investigated.
- Hashmi, A. Stephen K.,Ramamurthi, Tanuja Dondeti,Rominger, Frank
-
experimental part
p. 592 - 597
(2009/06/05)
-
- Convenient one-pot synthesis of (E)-β-aryl vinyl halides from benzyl bromides and dihalomethanes
-
(Chemical Equation Presented) (E)-β-Aryl vinyl iodides are synthesized in high yield with excellent stereoselectivity from benzyl bromides by a one-pot homologation/ stereoselective elimination procedure. Convenient conditions involving the anion of diiodomethane and an excess of base provide complete consumption of the benzyl bromide and elimination from a diiodoalkane intermediate. Similar conditions provide (E)-β-aryl vinyl chlorides and bromides by employing the anions of ICH2CI or CH2Br 2. The functional group tolerance and facile purification allows rapid access to a wide range of functionalized vinyl halides.
- Bull, James A.,Mousseau, James J.,Charette, Andre B.
-
body text
p. 5484 - 5488
(2009/06/06)
-
- Solid-phase oxidative halodecarboxylation of β-arylacrylic acids with the ceric ammonium nitrate-alkali halide system
-
The solid-phase oxidation of cinnamic, 4-methoxy- and 3,4-dimethoxycinnamic acids with Ce(NH4)2(NO3)6-MHal system leads to β-halostyrenes. Similar procedure in the absence of a metal halide results in a cleavage of the C=C bond giving the corresponding benzaldehydes.
- Nikishin,Sokova,Makhaev,Kapustina
-
experimental part
p. 118 - 123
(2009/04/13)
-
- The effect of vicinyl olefinic halogens on cross-coupling reactions using Pd(0) catalysis
-
(trans) 1-Chloro-2-iodoethylene (3), (trans) 1-bromo-2-iodoethylene (4), (trans) 1,2-diiodoethylene (5) and (cis and trans) 1,2-dibromoethylene (11) were reacted under Suzuki, Sonogashira and Negishi cross-coupling conditions using Pd catalysis to obtain mono coupled products. Only olefin template 3 provided the desired coupling products reliably under all reaction conditions. Compound 5 did not provide cross coupled products under any of the reaction conditions used. The Negishi reaction was the only one that worked for templates 4 and 11. Studies indicate that oxidative addition of the most reactive carbon-halogen bond to Pd(0) is followed by elimination of the second halide, when the second halide is a bromide or an iodide. This happens to a much lesser degree when the second halogen is a chloride. Graphical Abstract.
- Organ, Michael G.,Ghasemi, Haleh,Valente, Cory
-
p. 9453 - 9461
(2007/10/03)
-
- Iron-catalyzed transformations of 2-chloro-1,6-heptadienes
-
(Phosphane)iron complexes in the presence of excess trialkylaluminium reagents catalyze various transformations of 2-chloro-α,ω-dienes, depending on their structure. Most notably, in the cases of simple 2-chloro-1,6-heptadienes, cyclization with transfer of the alkyl group (Me and Et) from the corresponding trialkylaluminium compound was observed to give 2-alkyl-1-methylidenecyclopentanes. Reaction with 2-chloro-1,7-octadiene afforded the product of reductive dehalogenation. In the case of 2-chloro-4-aza-1,6-heptadiene a partial or complete hydrogenation of the double bonds was observed depending on the amount of trialkylaluminum reagent used. Interestingly, allyl(2-chloroallyl)malonate underwent C-C bond cleavage with the loss of an allyl group to give (2-chloroallyl)malonate. In the presence of ruthenium catalysts only reductive dehalogenation was observed. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Necas, David,Kotora, Martin,Cisarova, Ivana
-
p. 1280 - 1285
(2007/10/03)
-
- An Alternative Procedure in the Takai Reaction Using Chromium(III) Chloride Hexahydrate as a Convenient Source of Chromium(II)
-
An alternative procedure in the Takai reaction using chromium(III) chloride hexahydrate as the source of Cr(II) was performed. The use of zinc as Cr(III) reducer allowed us to carry out the iodovinylation of aldehydes in 63-99% yields. With the Garner and Dondoni aldehydes, these conditions along with a work-up using 4-t-butylpyridine allowed us to improve the yield of the corresponding vinyl iodide compared to the previous procedures.
- Auge, Jacques,Boucard, Valerie,Gil, Richard,Lubin-Germain, Nadege,Picard, Julien,Uziel, Jacques
-
p. 3733 - 3739
(2007/10/03)
-
- Halodecarboxylation of a,β-unsaturated carboxylic acids bearing aryl and styrenyl group at β-carbon with Oxone and sodium halide
-
Reaction of α,β-unsaturated carboxylic acid bearing aryl and styrenyl group at β-carbon with Oxone and sodium halide in aqueous acetonitrile afforded the corresponding haloalkenes.
- You,Lee
-
p. 105 - 107
(2007/10/03)
-
- Catalytic Hunsdiecker reaction and one-pot catalytic Hunsdiecker-Heck strategy: Synthesis of α,β-unsaturated aromatic halides, α- (dihalomethyl)benzenemethanols, 5-aryl-2,4-pentadienoic acids, dienoates and dienamides
-
The reaction of α,β-unsaturated aromatic (or heteroaromatic) carboxylic acids with N-halosuccinimides (1 equiv.) and catalytic tetrabutylammonium trifluoroacetate (0.2 equiv.) in dichloroethane results in facile halodecarboxylation affording the corresponding (E)-halides in good to excellent yields. A similar reaction, but with 2 equiv. of N-halosuccinimides in acetonitrile-water (1:1 v/v) results in the exclusive formation of the corresponding α-(dihalomethyl)benzenemethanols. Furthermore, a one-pot strategy has been developed combining catalytic Hunsdiecker reaction (using tetrabutylammonium trifluoroacetate in dichloroethane) and Heck coupling (using palladium acetate/triethylamine/triphenylantimony/dichloroethane) for the synthesis of 5-aryl-2,4-pentadienoic acids, esters and amides in moderate to good yields. The natural product piperine and pipergualamine has been synthesized via the above route. Mechanistic and theoretical studies (via AM1 calculations) provide a useful insight into the mechanism of the present halodecarboxylation reaction, suggesting an ionic pathway involving the attack of the halogenium ion across the carbon-carbon double bond, triggering the elimination of carbon dioxide. (C) 2000 Elsevier Science Ltd.
- Naskar, Dinabandhu,Roy, Sujit
-
p. 1369 - 1377
(2007/10/03)
-
- Thermal decomposition of alkenyliodonium tetrafluoroborates: A novel route to fluoroalkenes
-
Alkenyl(phenyl)iodonium tetrafluoroborates dissolved in chloroform, or in the solid state, decompose thermally at 60°C to yield fluoroalkenes and iodobenzene as major products via an S(N)1- or S(N)2-type reaction within the ion pair of the substrates. (C) 2000 Elsevier Science Ltd.
- Okuyama, Tadashi,Fujita, Morifumi,Gronheid, Roel,Lodder, Gerrit
-
p. 5125 - 5129
(2007/10/03)
-
- Chromium(ii)-mediated reactions of iodonium tetrafluoroborates with aldehydes: Umpolung of reactivity of diaryl-, alkenyl(aryl)-, and alkynyl(aryl)iodonium tetrafluoroborates
-
The method described herein allows us, for the first time, to perform umpolung of reactivity of diaryl-, alkenyl(aryl)-, and alkynyl(aryl)iodonium tetrafluoroborates. The method involves generation of organochromium(III) species via reaction of iodonium salts with anhydrous chromium dichloride, followed by their nucleophilic addition to aldehydes to yield alcohols. In contrast to the reaction of aryl and alkenyl halides with chromium dichloride, these iodonium salts are so active that organochromium(III) could be generated without using a nickel catalyst. Substituent effects of unsymmetrically substituted diaryliodonium salts on the product profiles are in good agreement with the reported mode of decomposition of the intermediate unsymmetrical diaryliodanyl radicals. Alkenyl(mesityl)iodonium tetrafluoroborates undergo exclusive alkenylation of aldehydes with no signs of the formation of an arylation product.
- Chen, Da-Wei,Ochiai, Masahito
-
p. 6804 - 6814
(2007/10/03)
-
- Is metal necessary in the Hunsdiecker-Borodin reaction?
-
The tetrabutylammonium trifluoroacetate (TBATFA) catalyzed conversion of α,β-unsaturated carboxylic acids to the corresponding halides with N-halosuccinimides in dichloroethane is reported as the first example of a metal-free catalytic version of the title reaction. The methodology was further employed for a facile synthesis of piperine.
- Naskar, Dinabandhu,Chowdhury, Shantanu,Roy, Sujit
-
p. 699 - 702
(2007/10/03)
-
- Reactions of Phenyl(styryl)iodonium Tetrafluoroborate with Halide Ions
-
Reactions of (E)-phenyl(styryl)iodonium tetrafluoroborate with chloride, bromide, and iodide ions are examined under various conditions. The products are those of substitution and elimination, involving (Z)-1-halo-2-phenylethene (2), phenylacetylene (3), and iodobenzene as main products as well as minor products of (E)-2 and 1-halo-1-phenylethene. Results of product analysis, UV absorption spectroscopy, and kinetic measurements are consistent with major pathways involving pre-equilibrium formation of halo-λ3-iodane and iodate intermediates, leading to the in-plane vinylic SN2 substitution to (Z)-2 and the intramolecular β-elimination to 3. The minor retained product (E)-2 is concluded to be formed through the vinylenebenzenium ion intermediate in 2,2,2-trifluoroethanol through the ligand coupling within the λ3iodane intermediate in acetonitrile. 1-Bromo-1-phenylethene is considered to be derived from 3 by reaction with HBr formed during the reaction.
- Okuyama, Tadashi,Oka, Hsjime,Ochiai, Masahito
-
p. 1915 - 1921
(2007/10/03)
-
- Mild conversion of alkenyl boronic acids to alkenyl halides with halosuccinimides
-
Reaction of alkenyl boronic acids with halosuccinimides (NIS, NBS or NCS) gives the corresponding alkenyl halides with the same geometry. This method is suitable for the synthesis of geometrically pure (E) and (Z) alkenyl halides, as well as 1,1- and 1,2-
- Petasis, Nicos A.,Zavialov, Ilia A.
-
p. 567 - 570
(2007/10/02)
-
- Highly cis-selective Wittig reactions employing α-heterosubstituted ylids
-
1-Alkenyl chlorides, bromides or iodides can be obtained with very high cis selectivities through Wittig reaction employing α-chloro, α-bromo α-iodo ylids derive from tris(2-methoxymethoxyphenyl)phospine. The corresponding α-methoxy substituted ylid produces enethers with again remarkably high cis/trans ratios. Palladium(II) catalyzed coupling of (Z)-1-iodo-1-heptene with ethyl acrylate affords ethyl (2E,4Z)-2-4-decadienoate, the Bartlett pear fragrance, with almost quantitative yield.
- Zhang, Xin-Ping,Schlosser, Manfred
-
p. 1925 - 1928
(2007/10/02)
-
- Photolysis of alkylhalodiazirines and direct observation of benzylchlorocarbene in cryogenic matrices
-
Photolysis of 3-benzyl-3-chlorodiazirine and its deuterated homologues 3-chloro-3-(phenyldideuteriomethyl)diazirine and 3-chloro-3-((pentadeuteriophenyl)methyl)diazirine has been investigated by means of IR and UV-vis spectroscopy in argon and xenon matri
- Wierlacher, Stefan,Sander, Wolfram,Uu, Michael T. H.
-
p. 8943 - 8953
(2007/10/02)
-
- Simple Stereospecific Syntheses of (E)-1-Chloro(or Bromo)alk-1-enes from Alk-1-ynes via Hydroboration
-
Stereochemically pure (E)-1-chloro(or bromo)alk-1-enes were obtained in sufficiently good yields from alk-1-ynes via hydroboration with dialkylborane followed by reactions with facile reagents; corresponding copper(II) halides, in the presence of a small
- Masuda, Yuzuru,Hoshi, Masayuki,Arase, Akira
-
p. 2723 - 2726
(2007/10/02)
-
- Benzylchlorocarbene: A New Ambiphile
-
Relative reactivites of benzylchlorocarbene towards electron-poor and electron-rich alkenes indicate the carbene to be ambiphilic.
- Liu, Michael T. H.,Suresh, Raghava, V.,Soundararajan, N.,Vessey, Edward G.
-
-
- CHEMICAL EVIDENCE FOR STABILIZATION OF ELECTRICALLY NEUTRAL DIVALENT CARBON BY POLAR SOLVENTS
-
Benzylhalocarbene generated in non-polar solvent is trapped readily by alkene, but the intermolecular process comes to compete poorly with the intramolecular process as the solvent polarity is increased.
- Tomioka, Hideo,Hayashi, Norihiro,Izawa, Yasuji
-
p. 695 - 698
(2007/10/02)
-
- Experimental and Theoretical Analysis of the Factors determining the Conformation and Stability of Singlet Carbene
-
Experimental and theoretical analyses of 1,2-H shifts in singlet carbene RCH2-C(:)-X (X = Cl, Ph) indicate that hyperconjugation of the carbene lone pair and the low-lying C-R ?* orbital of the β-substituent plays an important role in determining the relative population of the carbene conformers.
- Tomioka, Hideo,Sugiura, Tsugunori,Masumoto, Yoshinao,Izawa, Yasuji,Inagaki, Satoshi,Iwase, Koji
-
p. 693 - 695
(2007/10/02)
-
- Substituent and Temperature Effects on the Reactions of Benzylchlorocarbene with Alcohol
-
The insertion reaction of the para-substituted benzylchlorocarbenes with methanol shows a second-order dependence in methanol, but only a first-order dependence in ethylene glycol.The results are consistent with a mechanism whereby the carbene inserts into the O-H bond of the alcohol dimer or oligomer by electrophilic attack of the carbene on the oxigenone pair to produce a reversibly formed ylide intermediate.The effects of the substituents indicate that electron-releasing group favours rearrangement while electron-withdrawing group facilitates insertion.Photolysis of halogenodiazirines in methanol at low temperatures give rise to V-shaped Arrhenius behaviour and the importance of N2 in influencing the reactivity of the singlet halogenocarbene in the matrix is demonstrated.
- Liu, Michael T. H.,Subramanian, Ramasamy
-
p. 1233 - 1240
(2007/10/02)
-
- CARBON-CARBON BOND FORMING REACTION OF BIS(CHLOROMETHYL)SULFONE WITH CARBONYL COMPOUNDS: GENERAL ROUTE TO AROMATIC 2-CHLOROVINYL COMPOUNDS AND α-HYDROXYALDEHYDES
-
Bis(chloromethyl)sulfone (1) has been proved to be a useful reagent for the synthesis of aromatic 2-chlorovinyl compounds (4) from aromatic aldehydes and of α-hydroxyaldehydes (5) from aliphatic carbonyl compounds with one carbon prolongation.The sec-butyllithium-aided reaction of 1 with aromatic aldehydes gives 1,3-oxathiolane-3,3-dioxides (2) which are converted to 4 in good yields by thermolysis.On the other hand, the sodium hydride-aided reaction of 1 with aliphatic carbonyl compounds is favorable to the formation of chloromethylsulfonyloxiranes (3).Titanium tetrachloride has been found to be an efficient reagent for hydrolysis of 3 to 5.
- Nagashima, Enkou,Suzuki, Kunio,Ishikawa, Motoaki,Sekiya, Minoru
-
p. 1873 - 1879
(2007/10/02)
-
- REACTIVE INTERMEDIATES IN THE PHOTOLYSIS AND THERMOLYSIS OF 3-CHLORO-3-BENZYLDIAZIRINE
-
The photochemical and thermal decomposition of 3-chloro-3-benzyldiazirine have been studied in different reaction conditions.The decomposition gives rise to benzylchlorocarbene which can rearrange to E and Z chlorostyrene and/or react with the environment.In the presence of acetic acid the main product is 1-chloro-2-phenylethyl acetate.Experiments with acetic acid-d4 showed that some of the chlorostyrene is formed from the carbocation; other experiments conducted with tetramethylethylene as a carbene trapping agent show that the carbene is formed even in the presence of acetic acid.
- Liu, Michael T. H.,Chishti, Najmul H.,Tencer, Michael,Tomioka, Hideo,Izawa, Yasuji
-
p. 887 - 892
(2007/10/02)
-
- TEMPERATURE AND MATRIX EFFECTS ON COMPETITIVE INTERMOLECULAR AND INTRAMOLECULAR REACTION OF BENZYLCHLOROCARBENES IN ETHANOL
-
Benzylchlorocarbenes generated photolytically from diazirines in EtOH afford chlorostyrenes and acetals, whose distributions are sensitive to the reaction temperature.
- Tomioka, Hideo,Hayashi, Norihiro,Izawa, Yasuji,Liu, Michael T. H.
-
p. 4413 - 4416
(2007/10/02)
-
- Termolecular Trapping of Benzylchlorocarbene by Methanol
-
The trapping of benzylchlorocarbene by methanol is termolecular leading to a frequency factor of 2 x 105 l2 mol-2 s-1 and an activation energy of -4.5 kcal mol-1 (18.8 kJ mol-1).
- Liu, Michael T. H.,Subramanian, Ramasamy
-
p. 1062 - 1064
(2007/10/02)
-
- ATTEMPTED GENERATION OF HALOCARBENES: PROTODESILYLATION OF DIHALOMETHYLSILANES
-
Attempts to generate chlorocarbene or bromocarbene from (dichloromethyl)trimethylsilane and (dibromomethyl)trimethylsilane, respectively, under phase transfer conditions results in protodesilylation.The protodesilylation of 1,1-dihalosilanes under phase transfer conditions appears to be general.Phase transfer conditions are also useful for the protodesilylation of other organosilanes.
- Larson, Gerald L.,Cadiz, Carlos
-
p. 113 - 116
(2007/10/02)
-