- Manganese-catalyzed synthesis of cis-β-amino acid esters through organometallic C-H activation of ketimines
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Manganese-catalyzed C-H functionalization reactions of ketimines set the stage for the expedient synthesis of cis-β-amino acid esters through site- and regioselective alkene annulations. The organometallic C-H activation occurred efficiently with high fun
- Liu, Weiping,Zell, Daniel,John, Michael,Ackermann, Lutz
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- POLYMERIZATIONS OF ACETYLENES AND CYCLIC OLEFINS INDUCED BY METAL CARBYNES.
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trans-Bromotetracarbonyl(phenylmethylidyne)tungsten and related metal carbynes induce acetylenes and cycloalkenes to polymerize. The acetylenes include examples that are monosubstituted, disubstituted, and unsubstituted, as well as the first reported functionalized acetylenes in which the functional groups (the nitrile, ester, and halogen functions were studied) are not attached to the triple bond. The cycloalkenes yield polyalkenamers whose double bonds are largely cis. This last polymerization is speeded by the presence of oxygen. The stereochemistries of the polyacetylenes and the polynorbornenamer produced when the initiator is the metal carbyne are similar to those of the polymers produced when the initiator is pentacarbonyl(methoxyphenylmethylene)tungsten. A possible mechanism is presented to account for why the metal carbynes behave as though they were sources of reactive metal carbenes.
- Katz,Shih,Ying,Stuart
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- CONFORMATIONAL ORDER IN CRYSTALLINE STATES AND GELS OF ISOTACTIC, SYNDIOTACTIC AND ATACTIC POLYSTYRENES STUDIED BY VIBRATIONAL SPECTROSCOPY
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Stable conformations and their sequential order of isotactic (IPS), syndiotactic (SPS) and atactic polystyrenes (APS) in various aggregation states have been investigated by infrared (IR) spectroscopy, 13C NMR and X-ray diffraction.It has been demonstrated that the partially ordered skeletal conformation existing in IPS/CS2 gels of a (3/1) helix (TG) type having the pendant phenyl groups oriented in a disordered fashion, rather than the near-TT form proposed previously for IPS/decalin gels.The process of conformational change during gelation of IPS/CS2 and APS/CS2 systems has been followed by IR spectroscopy, and it has been concluded that the construction of regular sequences of a particular conformation promotes the gelation of both crystallizable and non-crystallizable polystyrenes.As-cast film specimens prepared from a chloroform solution are found to be a crystalline polymer-solvent complex (the γ phase) having a TTGG conformation.On heating, the γ phase transforms to a β phase at about 120 deg C, accompanied by removal of the solvent, while the TTGG conformation is retained.On further heating, the β phase transforms to an α1 or α2 phase at about 200 deg C accompanied by a change in conformation from TTGG to TT.The process of conformational change (in both type and sequence) during these phase transformations has been clarified by IR spectroscopy.
- Nakaoki, Takahiko,Kobayashi, Masamichi
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- Synthesis of Substituted 1-Hydroxy-2-Naphthaldehydes by Rhodium-Catalyzed C?H Bond Activation and Vinylene Transfer of Enaminones with Vinylene Carbonate
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The rhodium(III)-catalyzed C?H bond activation and vinylene transfer of enaminones with vinylene carbonate have been proposed for the synthesis of substituted 1-hydroxy-2-naphthaldehydes in 49–84% yields. Several preliminary mechanistic studies and hydrox
- Liu, Min,Yan, Kelu,Wen, Jiangwei,Liu, Weihua,Wang, Mingyu,Wang, Lina,Wang, Xiu
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supporting information
p. 512 - 517
(2021/12/09)
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- Rhodium-Catalyzed Annulation of Phenacyl Ammonium Salts with Propargylic Alcohols via a Sequential Dual C-H and a C-C Bond Activation: Modular Entry to Diverse Isochromenones
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Given their omnipresence in natural products and pharmaceuticals, isochromenone congeners are one of the most privileged scaffolds to synthetic chemists. Disclosed herein is a dual (ortho/meta) C-H and C-C activation of phenacyl ammonium salts (acylammonium as traceless directing group) toward annulation with propargylic alcohols to accomplish rapid access for novel isochromenones by means of rhodium catalysis from readily available starting materials. This operationally simple protocol features broad substrate scope and wide functional group tolerance. Importantly, the protocol circumvents the need of any stoichiometric metal oxidants and proceeds under aerobic conditions.
- Nanubolu, Jagadeesh Babu,Reddy Singam, Maneesh Kumar,Sridhar Reddy, Maddi,Suresh, Vavilapalli,Suri Babu, Undamatla
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supporting information
p. 7888 - 7893
(2021/10/25)
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- Experimental and Computational Studies of Palladium-Catalyzed Spirocyclization via a Narasaka-Heck/C(sp3or sp2)-H Activation Cascade Reaction
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The first synthesis of highly strained spirocyclobutane-pyrrolines via a palladium-catalyzed tandem Narasaka-Heck/C(sp3 or sp2)-H activation reaction is reported here. The key step in this transformation is the activation of a δ-C-H bond via an in situ generated σ-alkyl-Pd(II) species to form a five-membered spiro-palladacycle intermediate. The concerted metalation-deprotonation (CMD) process, rate-determining step, and energy barrier of the entire reaction were explored by density functional theory (DFT) calculations. Moreover, a series of control experiments was conducted to probe the rate-determining step and reversibility of the C(sp3)-H activation step.
- Wei, Wan-Xu,Li, Yuke,Wen, Ya-Ting,Li, Ming,Li, Xue-Song,Wang, Cui-Tian,Liu, Hong-Chao,Xia, Yu,Zhang, Bo-Sheng,Jiao, Rui-Qiang,Liang, Yong-Min
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supporting information
p. 7868 - 7875
(2021/05/27)
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- Rhodium-Catalyzed Spiro Indenyl Benzoxazine Synthesis via C-H Activation/Annulation of 3-Aryl-2H-Benzo[b][1,4]oxazines and Alkynes
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The rhodium (III)-catalyzed annulation of 3-Aryl-2H-Benzo[b][1,4]oxazines with alkynes via C–H activation has been developed. This reaction afforded a series of spiro indenyl benzoxazine in high yields under mild reaction condition with good functional group tolerance.
- Tan, Heng,Laishram, Ronibala Devi,Zhang, Xuexin,Shi, Guangrui,Li, Kangkui,Chen, Jingchao
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supporting information
p. 4542 - 4546
(2020/07/04)
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- Rh(III)-catalyzed synthesis of isoquinolines using the N-Cl bond of N-chloroimines as an internal oxidant
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The Rh(III)-catalyzed coupling of N-chloroimines with alkynes for the efficient synthesis of isoquinolines is reported. This represents the first use of the N-Cl bond of N-chloroimines as an internal oxidant for construction of the isoquinoline skeleton. The synthesis features atom and step economy, a green solvent (EtOH), mild reaction conditions, and a broad substrate scope.
- Chu, Benfa,Fang, Lili,Guo, Shan,Qi, Bing,Shi, Pengfei,Wang, Qi,Zhu, Jin
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supporting information
(2020/03/10)
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- Hydroxylamine-O-Sulfonic Acid (HOSA) as a Redox-Neutral Directing Group: Rhodium Catalyzed, Additive Free, One-Pot Synthesis of Isoquinolines from Arylketones
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A new application of hydroxylamine-O-sulfonic acid (HOSA) has been discovered whereby aromatic ketones react with HOSA and alkynes to form isoquinolines in the presence of a RhIII catalyst. This C–H/N–O annulation methodology gives excellent yields even without any silver additive, acid/base or metal oxidant. This is the first report wherein a directing group is simultaneously forming in situ, acting as acid additive, and also as an internal oxidant.
- Biswal, Pragati,Pati, Bedadyuti Vedvyas,Chebolu, Rajesh,Ghosh, Asit,Ravikumar
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supporting information
p. 1006 - 1014
(2020/02/15)
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- Rhodium-catalyzed C–H activation/cyclization of enaminones with sulfoxonium ylides toward polysubstituted naphthalenes
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A rhodium-catalyzed ortho-C–H functionalization and annulation between enaminones and sulfoxonium ylides was developed, affording a series of multi-substituted naphthalenes in good to moderate yields with excellent functional group compatibility. The proc
- Wang, Zhenlian,Xu, Huang
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supporting information
p. 664 - 667
(2019/02/06)
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- Spiro[indene-1,4′-oxa-zolidinones] Synthesis via Rh(III)-Catalyzed Coupling of 4-Phenyl-1,3-oxazol-2(3 H)-ones with Alkynes: A Redox-Neutral Approach
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Transition-metal-catalyzed C-H activation synthesis of heterocyclic spiro[4,4]nonanes has persistently witnessed the use of additional stoichiometric transition-metal oxidant when employing C=C bond as the spiro ring closure site. Herein, we have addressed the issue by reporting a redox-neutral strategy for spiro[indene-1,4′-oxa-zolidinones] synthesis via Rh(III)-catalyzed coupling of 4-phenyl-1,3-oxazol-2(3H)-ones with alkynes. The synthesis features a broad substrate scope and high regiospecificity.
- Liu, Zhongsu,Zhang, Wenjing,Guo, Shan,Zhu, Jin
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p. 11945 - 11957
(2019/10/02)
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- Pd-Catalyzed para-selective C-H difluoromethylation of aromatic carbonyls
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A novel palladium catalyzed highly para-selective C-H difluoromethylation of electron-deficient aromatic carbonyls was developed. Diverse substituted aromatic ketones and benzoates were selectively difluoromethylated at the remote para-site of carbonyl gr
- Mao, Yang-Jie,Wang, Bing-Xin,Wu, Qiu-Zi,Zhou, Kun,Lou, Shao-Jie,Xu, Dan-Qian
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supporting information
p. 2019 - 2022
(2019/02/19)
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- Rh(III)-Catalyzed Coupling of N-Chloroimines with α-Diazo-α-phosphonoacetates for the Synthesis of 2 H-Isoindoles
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We report herein the first use of N-chloroimines as effective synthons for directed C-H functionalization. Rh(III)-catalyzed coupling of N-chloroimines with α-diazo-α-phosphonoacetates allows for efficient dechlorinative/dephosphonative access to 2H-isoindoles. Further deesterification under Ni(II) catalysis enables the complete elimination of reactivity-assisting groups and full exposure of reactivity of C3 and N2 ring atoms for attaching structurally distinct appendages.
- Qi, Bing,Li, Lei,Wang, Qi,Zhang, Wenjing,Fang, Lili,Zhu, Jin
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supporting information
p. 6860 - 6863
(2019/09/12)
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- Cp*Co(III)-Catalyzed C?H Alkenylation of Aromatic Ketones with Alkenes
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Cost-effective and air-stable high-valent cobalt(III)-catalyzed weakly coordinating, ketone-directed regioselective mono-alkenylation of arenes and heteroarenes with alkenes is demonstrated. Various electron-rich and electron-deficient arenes are tolerate
- Sk, Md Raja,Bera, Sourav Sekhar,Maji, Modhu Sudan
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supporting information
p. 585 - 590
(2018/12/11)
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- Cp?-Free Cobalt-Catalyzed C-H Activation/Annulations by Traceless N, O-Bidentate Directing Group: Access to Isoquinolines
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N,O-Bidentate directing-enabled, traceless heterocycle synthesis is described via Cp?-free cobalt-catalyzed C-H activation/annulation. The weakly coordinating nature of the carboxylic acid was employed for the preparation of isoquinolines. Meanwhile, the N-O bond of the α-imino-oxy acid can serve as an internal oxidant. Terminal as well as internal alkynes can be efficiently applied to the catalytic system. This operationally simple approach shows a broad substrate scope with the products obtained in good to excellent yields.
- Li, Xiao-Cai,Du, Cong,Zhang, He,Niu, Jun-Long,Song, Mao-Ping
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supporting information
p. 2863 - 2866
(2019/04/17)
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- Aminopyrimidine compound, composition containing same and application thereof
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The invention discloses an aminopyrimidine compound as shown in a formula (I), preparation and application thereof, and particularly discloses an aminopyrimidine compound as shown in the formula (I),or polymorphism, pharmaceutically acceptable salt, prodr
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Paragraph 0162; 0165; 0167-0169
(2019/01/06)
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- Weakly Coordinating, Ketone-Directed Cp?Co(III)-Catalyzed C-H Allylation on Arenes and Indoles
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Weakly coordinating, ketone-directed, regioselective monoallylation of arenes and indoles is reported using a stable and cost-effective high-valent cobalt(III)-catalyst to access several important molecular building blocks. The allylation proceeds smoothl
- Sk, Md Raja,Bera, Sourav Sekhar,Maji, Modhu Sudan
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supporting information
p. 134 - 137
(2018/01/17)
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- A Ligand-Enabled Palladium-Catalyzed Highly para-Selective Difluoromethylation of Aromatic Ketones
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A practical and highly para-selective C?H difluoromethylation of aromatic ketones has been developed by employing tetrakis(triphenylphosphine)palladium(0) as the catalyst and triphenylphosphine as the ligand. In addition to general aromatic ketones, this
- Tu, Guangliang,Yuan, Chunchen,Li, Yuting,Zhang, Jingyu,Zhao, Yingsheng
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supporting information
p. 15597 - 15601
(2018/11/03)
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- Co(III)-Catalyzed Enaminone-Directed C-H Amidation for Quinolone Synthesis
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We report herein the development of a Co(III)-catalyzed enaminone-directed C-H amidation method for synthetic access to quinolones, an important heterocyclic scaffold for diverse pharmaceutically active structures. The C-H coupling with dioxazolones and subsequent deacylation of an installed amide group allow consecutive C-N coupling generation of quinolones with wide-ranging compatible substituent patterns.
- Shi, Pengfei,Wang, Lili,Chen, Kehao,Wang, Jie,Zhu, Jin
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supporting information
p. 2418 - 2421
(2017/05/12)
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- Rhodium-Catalyzed Cyclocarbonylation of Ketimines via C-H Bond Activation
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A novel rhodium-catalyzed oxidative cyclocarbonylation of ketimines via cleavage of two C-H bonds was established, which provided a direct and reliable method for the synthesis of a wide range of 3-methyleneisoindolin-1-ones with mostly moderate yields. P
- Gao, Bao,Liu, Song,Lan, Yu,Huang, Hanmin
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supporting information
p. 1480 - 1487
(2016/06/09)
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- Manganese(I)-Catalyzed Substitutive C?H Allylation
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The first manganese(I)-catalyzed C?H allylations with ample scope were achieved by carboxylate assistance. The highly selective C?H/C?O functionalizations proved viable with densely substituted allyl carbonates, and the organometallic C?H allylation strategy set the stage for expedient late-stage diversification with excellent levels of positional selectivity.
- Liu, Weiping,Richter, Sven C.,Zhang, Yujiao,Ackermann, Lutz
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supporting information
p. 7747 - 7750
(2016/07/07)
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- Enaminones as Synthons for a Directed C?H Functionalization: RhIII-Catalyzed Synthesis of Naphthalenes
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The use of enaminones as effective synthons for a directed C?H functionalization is reported. Proof-of-concept protocols have been developed for the RhIII-catalyzed synthesis of naphthalenes, based on the coupling of enaminones with either alkynes or α-diazo-β-ketoesters. Two inherently reactive functionalities (hydroxy and aldehyde groups) are integrated into the newly formed cyclic framework and a broad range of substituents are tolerated, rendering target products readily available for further elaboration.
- Zhou, Shuguang,Wang, Jinhu,Wang, Lili,Song, Chao,Chen, Kehao,Zhu, Jin
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supporting information
p. 9384 - 9388
(2016/08/05)
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- Bidentate Directing-Enabled, Traceless Heterocycle Synthesis: Cobalt-Catalyzed Access to Isoquinolines
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Traceless heterocycle synthesis based on transition-metal-catalyzed C-H functionalization is synthetically appealing but has been realized only in monodentate directing systems. Bidentate directing systems allow for the achievement of high catalytic reactivity without the need for a high-cost privileged ligand. The first bidentate directing-enabled, traceless heterocycle synthesis is demonstrated in the cobalt-catalyzed synthesis of isoquinolines via 2-hydrazinylpyridine-directed C-H coupling/cyclization with alkynes. Convenient directing group installation through a ubiquitously present ketone group allows synthetic elaboration for complex molecules.
- Zhou, Shuguang,Wang, Mingyang,Wang, Lili,Chen, Kehao,Wang, Jinhu,Song, Chao,Zhu, Jin
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supporting information
p. 5632 - 5635
(2016/11/17)
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- Easy Access to 1-Amino and 1-Carbon Substituted Isoquinolines via Cobalt-Catalyzed C - H/N - O Bond Activation
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A green atom-economical method for the synthesis of highly functionalized 1-amino and 1-carbon substituted isoquinolines from the reaction of N′-hydroxybenzimidamides and aryl ketoximes, respectively, with alkynes via pentamethylcyclopentadienylcobalt(III)-catalyzed C - H/N - O bond activation is described. The external oxidant-free annulation reaction uses the =NOH moiety in N′-hydroxybenzimidamides or N-aromatic ketone oximes as the directing group and internal oxidant. This first row transition metal-catalyzed annulation serves as an efficient alternative for the synthesis of isoquinolines, as water is the only by-product and expensive noble metals such as rhodium(III), iridium(III), palladium(II), and ruthenium(II) are not required. The reaction proceeds via C - H activation, alkyne insertion, reductive elimination, and N - O activation.
- Muralirajan, Krishnamoorthy,Kuppusamy, Ramajayam,Prakash, Sekar,Cheng, Chien-Hong
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supporting information
p. 774 - 783
(2016/03/09)
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- Cobalt(III)-Catalyzed C-H/N-O Functionalizations: Isohypsic Access to Isoquinolines
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C-H/N-O functionalizations by cobalt(III) catalysis allowed the expedient synthesis of a broad range of isoquinolines. Thus, internal and challenging terminal alkynes proved to be viable substrates for an isohypsic annulation, which was shown to proceed by a facile C-H cobaltation.
- Wang, Hui,Koeller, Julian,Liu, Weiping,Ackermann, Lutz
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supporting information
p. 15525 - 15528
(2015/11/03)
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- Iron-Catalyzed Cross-Coupling of Alkenyl Acetates
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Stable C-O linkages are generally unreactive in cross-coupling reactions which mostly employ more electrophilic halides or activated esters (triflates, tosylates). Acetates are cheap and easily accessible electrophiles but have not been used in cross-couplings because the strong C-O bond and high propensity to engage in unwanted acetylation and deprotonation. Reported herein is a selective iron-catalyzed cross-coupling of diverse alkenyl acetates, and it operates under mild reaction conditions (0 C, 2 h) with a ligand-free catalyst (1-2 mol%). Iron clad: Acetates are underutilized electrophiles in metal-catalyzed cross-coupling reactions because of the strong alkenyl C-O bond and their propensity to engage in unwanted reactions. Combination of a ligand-free low-valent Fe catalyst with nucleophilic organomagnesium reagents, low temperature, and short reaction times results in highly selective cross-couplings with alkenyl acetates.
- G?rtner, Dominik,Stein, André Luiz,Grupe, Sabine,Arp, Johannes,Von Wangelin, Axel Jacobi
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supporting information
p. 10545 - 10549
(2015/09/02)
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- The "kinetic capture" of an acylium ion from live aluminum chloride promoted Friedel-Crafts acylation reactions
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AlCl3 promoted Friedel-Crafts acylation between 4-tert-butylbenzoyl chloride and mesitylene was investigated. The donor-acceptor complex was observed as the major species. Kinetic investigation demonstrated that the reaction was first-order on the donor-acceptor complex and zero-order on ArH, suggesting that the donor-acceptor complex was not the true reactive species. However, the acylium ion was almost invisible with a fairly low concentration under live reaction conditions. It was approved as the true reactive species through kinetic data ("kinetic capture") in the AlCl3 promoted Friedel-Crafts acylation reaction.
- Huang, Zhiliang,Jin, Liqun,Han, Heyou,Lei, Aiwen
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p. 1810 - 1814
(2013/04/10)
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- Palladium-catalyzed chelation-assisted aromatic C-H nitration: Regiospecific synthesis of nitroarenes free from the effect of the orientation rules
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A palladium-catalyzed chelation-assisted ortho-nitration of aryl C-H bond is described. A range of azaarenes such as 2-arylquinoxalines, pyridines, quinoline, and pyrazoles were nitrated with excellent chemo- and regioselectivity. Using the O-methyl oximyl group as a removable directing group, the regiospecific synthesis of a variety of o-nitro aryl ketones was achieved starting from aryl ketones via a three-step process involving the Pd-catalyzed ipso-nitration of C-H bond as a key step. Mechanistic investigations support a silver-mediated radical mechanism involving Pd((II/III) and/or Pd(II/IV) catalytic cycles under oxidizing conditions.
- Zhang, Wei,Lou, Shaojie,Liu, Yunkui,Xu, Zhenyuan
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p. 5932 - 5948
(2013/07/26)
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- Cobalt-catalyzed ortho -arylation of aromatic imines with aryl chlorides
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An ortho-arylation reaction of aromatic imines with aryl chlorides has been achieved using a cobalt-N-heterocyclic carbene catalyst in combination with a neopentyl Grignard reagent. The reaction takes place at room temperature to afford biaryl products in moderate to good yields.
- Gao, Ke,Lee, Pin-Sheng,Long, Chong,Yoshikai, Naohiko
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supporting information; experimental part
p. 4234 - 4237
(2012/09/22)
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- Regiospecific synthesis of nitroarenes by palladium-catalyzed nitrogen-donor-directed aromatic C-H nitration
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Nitration of N-heteroaromatics: The first example of palladium-catalyzed direct ortho-nitration of aryl C-H bonds is described. A range of azaarenes, such as 2-arylquinoxalines, pyridines, pyrazoles, and O-methyl oximes, were nitrated with excellent chemo- and regioselectivity (see scheme; DCE=1,2-dichloroethane). Preliminary mechanistic investigations support a silver-mediated radical mechanism involving palladium(II/III) and/or palladium(II/IV) catalytic cycles under oxidizing conditions. Copyright
- Liu, Yun-Kui,Lou, Shao-Jie,Xu, Dan-Qian,Xu, Zhen-Yuan
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supporting information; experimental part
p. 13590 - 13593
(2011/03/18)
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- Novel anti-Markovnikov regioselectivity in the Wacker reaction of styrenes
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The Wacker reaction is one of the longest known palladium-catalysed organic transformations, and in the vast majority of cases proceeds with Markovnikov regioselectivity. Palladium(II)-mediated oxidation of styrenes was examined and in the absence of reoxidants was found to proceed in an anti-Markovnikov sense, giving aldehydes. Studies on the mechanism of this unusual transformation were carried out, and indicate the possible involvement of a η4-palladium-styrene complex. With a heteropolyacid as the terminal oxidant, oxidation of styrene to give the anti-Markovnikov aldehyde as the major product was found to be catalytic.
- Wright, Joseph A.,Gaunt, Matthew J.,Spencer, Jonathan B.
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p. 949 - 955
(2007/10/03)
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- Chemically-induced discotic liquid crystals. Structural, studies with NMR spectroscopy
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The use of nuclear magnetic resonance (NMR) spectrometry for the structural studies of chemically-induced discotic liquid crystals was discussed. The synthesis of the phase inductor with two deutrons in the phenyl ring was accomplished in a single step using the catalytic exchange procedure. The reaction was quenched by the addition of 5 ml D2O, the organic layer was left to evaporate and 0.38 g of the product was obtained. The degree of deuteriation was found by proton NMR to be approximately 70%.
- Hughes,Luckhurst,Praefcke,Singer,Tearle
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p. 187 - 225
(2007/10/03)
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- Toward the creation of NMR databases in chiral solvents for assignments of relative and absolute stereochemistry: proof of concept.
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[structure: see text] An NMR database approach in a chiral solvent allows us to predict both relative and absolute stereochemistry of an unknown compound without degradation and/or derivatization. N,alpha-Dimethylbenzylamine (DMBA) is a suitable solvent for this purpose. Using the C.5-C.10 portion of oasomycin A, the feasibility and reliability of this approach is demonstrated.
- Kobayashi,Hayashi,Tan,Kishi
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p. 2245 - 2248
(2007/10/03)
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- Characterization, via ESR Spectroscopy, of Radical Intermediates in the Photooxidation of Arylcarbinols by Ceric Ammonium Nitrate
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The photooxidation by ceric ammonium nitrate (CAN) of several aryl and naphthylcarbinols has been studied by means of ESR spectroscopy. For all the investigated arylcarbinols, but not for the naphthyl derivatives, it has been possible to detect radical intermediates deriving from the parent alkoxyl radicals. In particular, in the photooxidation of 1,1-diphenylethanol, a bridged-radical intermediate has been detected. The assignment has been validated through experiments with two different labeled compounds: the 1,1-[2′, 3′, 4′, 5′, 6′, 2″, 3″, 4″, 5″, 6″-2H10]diphenylethanol and the 1,1-diphenyl[2, 2, 2-2H3]ethanol. A similar bridged radical has been found to be formed in the photooxidation of triphenylmethanol, while, for the 1,1-diphenylpropanol, the only detectable species has been the ethyl radical deriving from a competitive β-scission process. Finally, for the 2-phenylpropan-2-ol (cumyl alcohol), two radical species have been identified: the methyl, deriving from the β-scission process, and the cyanomethylene, deriving from H-abstraction of the cumyloxyl radical from the solvent. A kinetic study on the competition of the two processes has also been conducted and the parameters of the Arrhenius equation for the latter process have been estimated.
- Grossi, Loris,Strazzari, Samantha
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p. 2748 - 2754
(2007/10/03)
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- The Mechanism of Two Reactions leading to Isomeric 2-(N,N-Disubstituted Amino)thiazol-5-yl Ketones
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A study has been made of the condensations between N-acyl-N',N'-disubstituted thioureas and α-halogeno ketones , and between N,N-disubstituted thioureas and 2-bromo-1,3-diketones .The mechanistic details were elucidated by usi
- Challacombe, Katherine,Leach, Susan E.,Plackett, Simon J.,Meakins, G. Denis
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p. 2213 - 2218
(2007/10/02)
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- Base Catalysed Rearrangements involving Ylide Intermediates. Part 15. The Machanism of the Stevens Rearrangement
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The Stevens rearrangement of acyl-stabilised ammonium ylides has been investigated with regard to stereoselectivity, intramolecularity and the formation of products in addition to the rearrangement product.A detailed study of the effects of reaction conditions upon the rearrangement of the ylide derived from the salt (13) has shown that the stereoselectivity (retention of the configuration of the chiral migrating group) and intramolecularity decrease as solvent viscosity decreases.The rearrangement of the salt (13) in water at 0 deg C is essentially intramolecular with virtually complete retention of the configuration of the migrating group.These results, together with the isolation of products that can be rationalised on the basis of random free-radical coupling, indicate that the rearrangement of acyl-stabilised ammonium ylides normally involves a radical pair mechanism.
- Ollis, W. David,Rey, Max,Sutherland, Ian O.
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p. 1009 - 1027
(2007/10/02)
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- Infrared studies of acetophenone and its deuterated derivatives
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The i.r. spectra of acetophenone and their deuterated analogues (-d3, -d5, -d8) in the liquid-phase have been recorded and analyzed in the range 4000-130 cm-1.Additional data on band contours in the gas-phase, in conjuction with the deuteration effects, allowed us to assign all the fundamentals for the four isotopic varieties.A valence force field calculation was also used to support the proposed assignment.
- Gambi, A.,Giorgianni, S.,Passerini, A.,Visinoni, R.,Ghersetti, S.
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p. 871 - 878
(2007/10/02)
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