1006-27-5Relevant articles and documents
Indanetricarbonylchromium: the effects of 1-syn- and 1-anti substituents on the regioselectivity of nucleophilic addition. Crystal structures of 1-syn- and 1-anti-methoxyindanetricarbonylchromium
Ohlsson, Bengt,Ullenius, Christina,Jagner, Susan,Grivet, Chantal,Wenger, Eric,Kuendig, E. Peter
, p. 243 - 268 (1989)
A series of diastereomeric syn and anti Cr(CO)3 complexes of 1-substituted indanes have been prepared by thermolysis of Cr(CO)6 or by arene exchange with naphthalene-Cr(CO)3 (3).The regioselectivity of nucleophilic addition of α-nitrile carbon nucleophiles to syn and anti 1-R-indane Cr(CO)3 complexes (R=OMe 4, Me 10) has been investigated and compared with that of analogous reactions with indaneCr(CO)3 (1).The results of an X-ray study of syn- and anti-4 are presented.Nucleophilic additions are shown to be sensitive to the steric and electronic effects of the benzylic substituent and the nucleophile.When the reaction mixtures are warmed to 0 deg C, equilibration of the regioisomeric cyclohexadienyl intermediates takes place.
Functional-Group-Directed Diastereoselective Hydrogenation of Aromatic Compounds. 21
Ranade, Vidyadhar S.,Consiglio, Giambattista,Prins, Roel
, p. 1132 - 1138 (2000)
Diastereoselective liquid-phase hydrogenation of a series of monosubstituted indan substrates was studied on supported rhodium catalysts. Predominantly the cis-cis diastereomer, obtained by hydrogenation from the diastereoface opposite the substituent at the stereogenic center, and the cis-trans diastereomer, obtained by hydrogenation from the diastereoface on the same side as the substituent, were formed. The diastereoselectivity depends on the balance between steric repulsion and electronic attraction of the substituent with the surface of the catalyst. For alkoxy and carboxyl groups (acid, methyl ester, and amide), the steric repulsion dominated and the cis-cis diastereomer was obtained with moderately high selectivity. The diastereoselectivity obtained in the hydrogenation was influenced by the addition of bases to the reaction mixture. Addition of triethylamine caused a small increase in the selectivity to the cis-cis diastereomer in some substrates, whereas the addition of NaOH significantly increased the selectivity toward the cis-trans isomer in all substrates.
Conformational effects on the excited state 1,2-hydrogen migration in alkyldiazomethanes
Reed, Sasha C.,Modarelli, David A.
, p. 7209 - 7212 (1996)
Excited state rearrangements of alkyldiazo compounds are well-known. In particular, 1,2-hydrogen migrations to give carbene products are common. In this communication we provide evidence showing the migration in the diazo excited state is dependent upon the dihedral angle formed between the migrating hydrogen and the diazo carbon.
Intramolecular reactivity of functionalized arylcarbenes: 7-Alkenyloxy-1-indanylidenes
Gotzhein, Frank,Kirmse, Wolfgang
, p. 1377 - 1380 (1997)
1,2-H shift is the only intramolecular reaction of 7-(1-propenyloxy)-1-indanylidenes (8) whereas 7-(2-propenyloxy)-1-indanylidene (13) and 7-(2-butenyloxy)-1-indanylidenes (19) undergo addition to the side-chain C=C bond and 1,2-H shifts competitively. Owing to the small RCR bond angle of 1-indanylidenes, the intramolecular chemistry is dominated by the singlet state even if the carbenes are generated by triplet-sensitized photolysis (k(TS) > k(T)).
Redox-Switchable Hydroelementation of a Cobalt Complex Supported by a Ferrocene-Based Ligand
Shepard, Scott M.,Diaconescu, Paula L.
, p. 2446 - 2453 (2016)
The first crystallographically characterized tetrahedral cobalt salen (salen = N,N′-ethylenesalicylimine) complex was synthesized by using a 1,1′-ferrocene derivative, salfen (salfen = 1,1′- di(2,4-di-tert-butyl-6-salicylimine)ferrocene). The complex undergoes two oxidation events at low potentials, which were assigned as ligand centered by comparison to the corresponding zinc complex. The cobalt complex was found to catalyze the hydroalkoxylation of styrenes, similarly to related square planar cobalt salen complexes, likely due to its fluxional behavior in alcoholic solvents. Furthermore, the one-electron-oxidized species was found to be inactive toward hydroalkoxylation. Thus, the hydroalkoxylation reactivity could be turned on/off in situ by redox chemistry.
Chemoselective and direct functionalization of methyl benzyl ethers and unsymmetrical dibenzyl ethers by using iron trichloride
Sawama, Yoshinari,Goto, Ryota,Nagata, Saori,Shishido, Yuko,Monguchi, Yasunari,Sajiki, Hironao
supporting information, p. 2631 - 2636 (2014/03/21)
Methyl and benzyl ethers are widely utilized as protected alcohols due to their chemical stability, such as the low reactivity of the methoxy and benzyloxy groups as leaving groups under nucleophilic conditions. We have established the direct azidation of chemically stable methyl and benzyl ethers derived from secondary and tertiary benzyl alcohols. The present azidation chemoselectively proceeds at the secondary or tertiary benzylic positions of methyl benzyl ethers or unsymmetrical dibenzyl ethers and is also applicable to direct allylation, alkynylation, and cyanation reactions, as well as the azidation. The present methodologies provide not only a novel chemoselectivity but also the advantage of shortened synthetic steps, due to the direct process without the deprotection of the methyl and benzyl ethers. Ethers exchanged: Methyl and benzyl ethers are chemically stable and generally tolerant under nucleophilic substitution conditions. Iron-catalyzed direct functionalizations (e.g., azidation, allylation, alkynylation, and cyanation) of methyl and benzyl ethers derived from secondary and tertiary benzyl alcohols were established with excellent regioselectivities (see scheme; PG: protecting group; Bn: benzyl; Nu: nucleophile; TMS: trimethylsilyl). Copyright
Hydroalkoxylation of unactivated olefins with carbon radicals and carbocation species as key intermediates
Shigehisa, Hiroki,Aoki, Tatsuya,Yamaguchi, Sumiko,Shimizu, Nao,Hiroya, Kou
supporting information, p. 10306 - 10309 (2013/08/23)
A unique Markovnikov hydroalkoxylation of unactivated olefins with a cobalt complex, silane, and N-fluoropyridinium salt is reported. Further optimization of reaction conditions yielded high functional group tolerance and versatility of alcoholic solvent employed, including methanol, i-propanol, and t-butanol. Use of trifluorotoluene as a solvent made the use of alcohol in stoichiometric amount possible. Mechanistic insight into this novel catalytic system is also discussed. Experimental results suggest that catalysis involves both carbon radical and carbocation intermediates.
Synthesis and chemistry of endoperoxides derived from 3,4-dihydroazulen-1(2H)-one: An entry to cyclopentane-anellated tropone derivatives
Celik, Murat,Akbulut, Nihat,Balci, Metin
, p. 3131 - 3138 (2007/10/03)
Reduction of trienone 1 and subsequent treatment with acid in MeOH furnished 1-methoxy-1,2,3,4-tetrahydroazulene (13). Photo-oxygenation of 13 provided the two bicyclic endoperoxides 14 and 15. Pyrolysis of 14 and 15 gave the corresponding bis-epoxides 17 and 18, which have been synthesized also upon treatment with a catalytic amount of CoTPP (TPP = tetraphenylporphyrin). That an unusual endoperoxide-endoperoxide rearrangement has not been observed strongly supports the assumption that the carbonyl group in 2-4 is responsible for this unprecedented endoperoxide-endoperoxide rearrangement. Treatment of the endoperoxides 14 and 15 with a catalytic amount of Et3N at O° provided the azulenones 22 and 23 in high yield. Attempted cleavage of the O - O peroxide linkage in 14 and 15 with thiourea resulted, contrary lo our expectation, in the formation of 22 and 23. That thiourea acts as a base instead of a reducing reagent has been observed for the first time in peroxide chemistry.
Ruthenium-catalyzed oxidation of alkanes with tert-butyl hydroperoxide and peracetic acid
Murahashi,Komiya,Oda,Kuwabara,Naota
, p. 9186 - 9193 (2007/10/03)
The ruthenium-catalyzed oxidation of alkanes with tert-butyl hydroperoxide and peracetic acid gives the corresponding ketones and alcohols highly efficiently at room temperature. The former catalytic system, RuCl2(PPh3)3-t-BuOOH, is preferable to the oxidation of alkylated arenes to give aryl ketones. The latter system, Ru/C-CH3CO3H, is suitable especially for the synthesis of ketones and alcohols from alkanes. The ruthenium-catalyzed oxidation of cyclohexane with CH3CO3H in trifluoroacetic acid/CH2Cl2 at room temperature gave cyclohexyl trifluoroacetate and cyclohexanone with 90% conversion and 90% selectivity (85:15). The mechanistic study indicates that these catalytic oxidations of hydrocarbons involve oxo-ruthenium species as key intermediates.
The Photochemistry of Conformationally Rigid Benzylic Esters: 2,2-Dimethyl-1-indanyl Acetates and Pivalates
Pincock, J. A.,Wedge, P. J.
, p. 4067 - 4076 (2007/10/02)
The photochemistry, in methanol, of substituted 2,2-dimethyl-1-indanyl acetates 9a-c and pivalates 10a-c has been studied.In agreement with previous studies on benzylic esters, the results show that the substituents change the yield of products derived from the ion pair.The mechanistic conclusion reached is that the substituents change the oxidation potential of the indanyl radicals and thus the rate constant of electron transfer for converting the radical pair to the ion pair.The results also reveal two other substituent effects.First, substituents can increase the overall efficiency of the photoreaction by enhancing homolytic cleavage.The second effect is conformational.In compounds where the bond that is cleaving is conformationally mobile, such as the C-O bond in benzylic esters, substituents on the ring can change the population of the reactive conformer and thus the overall efficiency of the reaction.For the indanyl acetate esters, the difference in excited-state reaction rate between the m- and p-methoxy substituted ester is 15:1.For the m- and p-methoxy substituted benzyl acetates, this difference in reaction rate is 48:1.The larger difference in reaction rate for the conformationally mobile benzylic esters is attributed to a higher population of the unreactive conformer for the p-methoxy substituted ester.
