36322-03-9Relevant academic research and scientific papers
Synthesis, Structural Characterization, and Reactivity of a Fluorene-Based Calcium Oxycyclopentadienide Complex
Wei, Baosheng,Li, Heng,Zhang, Wen-Xiong,Xi, Zhenfeng
, p. 1339 - 1344 (2015)
Direct deprotonation of 9-fluorenol with Ca[N(SiMe3)2]2 efficiently generated a fluorene-based calcium oxycyclopentadienide complex, which is the first alkaline earth metal complex containing an oxycyclopentadienyl dianion ligand. The η5, η1, and η2 interactions between the oxycyclopentadienyl dianion ligand and the calcium center were observed in the solid state. The calcium oxycyclopentadienide complex displayed reductive character and multiple reactive sites. Its reactivity toward a range of electrophiles, especially acid chlorides, was investigated and discussed in detail. A wide variety of fluorene derivatives were synthesized. (Chemical Equation Presented).
Ligand-Free Ru-Catalyzed Direct sp3 C-H Alkylation of Fluorene Using Alcohols
Shaikh, Moseen A.,Agalave, Sandip G.,Ubale, Akash S.,Gnanaprakasam, Boopathy
, p. 2277 - 2290 (2020/02/04)
The sp3 C-H alkylation of 9H-fluorene using alcohol and a Ru catalyst via the borrowing hydrogen concept has been described. This reaction was catalyzed by the [Ru(p-cymene)Cl2]2 complex (3 mol %) and exhibited a broad reaction scope with different alcohols, allowing primary and secondary alcohols to be employed as nonhazardous and greener alkylating agents with the formation of environmentally benign water as a byproduct. A variety of 9H-fluorene underwent selective and exclusive mono-C9-alkylation with primary alcohols in good to excellent isolated yield (26 examples, 50-92% yield), whereas this reaction with secondary alcohols in the absence of any external oxidants furnished the tetrasubstituted alkene as the major product. Furthermore, a base-mediated C-H hydroxylation of the synthesized 9H-fluorene derivatives afforded 9H-hydroxy-functionalized quaternary fluorene derivatives in excellent yield.
Manganese-Catalyzed Synthesis of Quaternary Peroxides: Application in Catalytic Deperoxidation and Rearrangement Reactions
Chaudhari, Moreshwar B.,Gnanaprakasam, Boopathy,Shaikh, Moseen A.,Ubale, Akash S.
, p. 10488 - 10503 (2020/09/23)
Highly efficient, selective, and direct C-H peroxidation of 9-substituted fluorenes has been achieved using a Mn-2,2′-bipyridine catalyst via radical-radical cross-coupling. Moreover, this method effectively promotes the vicinal bisperoxidation of sterically hindered various substituted arylidene-9H-fluorene/arylideneindolin-2-one derivatives to afford highly substituted bisperoxides with high selectivity over the oxidative cleavage of Ca C bond that usually forms the ketone of an aldehyde. Furthermore, a new approach for the synthesis of (Z)-6-benzylidene-6H-benzo[c]chromene has been achieved via an acid-catalyzed skeletal rearrangement of these peroxides. For the first time, unlike O-O bond cleavage, reductive C-O bond cleavage in peroxides using the Pd catalyst and H2 is described, which enables the reversible reaction to afford exclusively deperoxidized products. A detailed mechanism for peroxidation, molecular rearrangement, and deperoxidation has been proposed with preliminary experimental evidences.
Aldehydes as alkyl carbanion equivalents for additions to carbonyl compounds
Wang, Haining,Dai, Xi-Jie,Li, Chao-Jun
, p. 374 - 378 (2017/04/03)
Nucleophilic addition reactions of organometallic reagents to carbonyl compounds for carbon-carbon bond construction have played a pivotal role in modern chemistry. However, this reaction's reliance on petroleum-derived chemical feedstocks and a stoichiometric quantity of metal have prompted the development of many carbanion equivalents and catalytic metal alternatives. Here, we show that naturally occurring carbonyls can be used as latent alkyl carbanion equivalents for additions to carbonyl compounds, via reductive polarity reversal. Such 'umpolung' reactivity is facilitated by a ruthenium catalyst and diphosphine ligand under mild conditions, delivering synthetically valuable secondary and tertiary alcohols in up to 98% yield. The unique chemoselectivity exhibited by carbonyl-derived carbanion equivalents is demonstrated by their tolerance to protic reaction media and good functional group compatibility. Enantioenriched tertiary alcohols can also be accessed with the aid of chiral ligands, albeit with moderate stereocontrol. Such carbonyl-derived carbanion equivalents are anticipated to find broad utility in chemical bond formation.
Iodine-catalyzed transformation of aryl-substituted alcohols under solvent-free and highly concentrated reaction conditions
Jereb, Marjan,Vra?i?, Dejan
, p. 747 - 762 (2018/01/17)
Iodine-catalyzed transformations of alcohols under solvent-free reaction conditions (SFRC) and under highly concentrated reaction conditions (HCRC) in the presence of various solvents were studied in order to gain insight into the behavior of the reaction intermediates under these conditions. Dimerization, dehydration and substitution were the three types of transformations observed with benzylic alcohols. Dimerization and substitution reactions were predominant in the case of primary- and secondary alcohols, whereas dehydration prevailed in the case of tertiary alcohols. The relative reactivity of substituted 1-phenylethanols in I2-catalyzed dimerization under SFRC provided a good Hammett plot ρ+ = -2.8 (r2 = 0.98), suggesting the presence of electron-deficient intermediates with a certain degree of developed charge in the rate-determining step.
Radical-radical cross coupling reactions of photo-excited fluorenones
Sharma, Simmi,Sultan, Shaista,Devari, Shekaraiah,Shah, Bhahwal Ali
supporting information, p. 9645 - 9649 (2016/10/22)
Radical-radical cross coupling reactions of photoexcited 9-fluorenones have been accomplished for the first time, leading to the synthesis of 9-alkyl, pyrollidinyl and spiro-THF derivatives of 9-fluorenones. The method also reveals, for the first time, th
Tricylic amino-acid derivatives
-
, (2008/06/13)
Described herein are compounds which have the general formula: or a prodrug or pharmaceutically acceptable salt, solvate or hydrate thereof wherein: R1 is selected from the group consisting of H, alkyl and the counter ion for a basic addition salt; X is selected from the group consisting of CR9R10, S, O, SO, SO2, NH and N-alkyl; R2, R3, R4, R9 and R10 are independently selected from the group consisting of H and alkyl; R5 and R6 are independently selected from the group consisting of H, alkyl and phenyl, or, alternatively, R5 and R6 together may form a methylene group or a 3- to 6-membered a spirocyclic group; wherein, when X is CR9R10, one or both pairs of R5 and R9 or R6 and R10 may join to form a double or triple bond R7 is selected from the group consisting of Formula II-V: which are all optionally substituted, at nodes other than R8, with 1-4 substituents independently selected from the group consisting of alkyl, halo, aryl (which may be substituted as for R8), trifluoromethyl, trifluoromethoxy, nitro, cyano, amino, mono-alkylamino, di-alkylamino, alkoxycarbonyl, alkylcarbonyl, alkoxythiocarbonyl, alkylthiocarbonyl, alkoxy, alkylS-, phenoxy, -SO2NH2, -SO2NHalkyl, -SO2N(alkyl)2 and 1,2-methylenedioxy; and wherein any of the benzo-fused rings in structures II to V may be replaced by a 5- or 6-membered heterocyclic ring selected from the group consisting of pyridine, thiophene, furan and pyrrole; wherein R8 is selected from the group consisting of H, alkyl, benzyl, cycloalkyl, indanyl and an optionally substituted aryl group, wherein the optional substituents are independently selected from 1-4 members of the group consisting of alkyl, halo, aryl, trifluoromethyl, trifluoromethoxy, nitro, cyano, amino, mono-alkylamino, di-alkylamino, alkoxycarbonyl, alkylcarbonyl, alkoxythiocarbonyl, alkylthiocarbonyl, alkoxy, alkylS-, phenoxy, -SO2NH2, -SO2NHalkyl, -SO2N(alkyl)2 and 1,2-methylenedioxy; -represents a single or double bond; Y is selected from the group consisting of O, S, SO, NH, N-alkyl, CH2, CH-alkyl, C(alkyl)2, and C=O; Z is selected from the group consisting of CH2, O, S, NH and N-alkyl when-is a single bond; Z is selected from the group consisting of CH and N when-is a double bond. Also described is the use of these compounds as pharmaceuticals.
Synthesis of a 9-fluorenone derived β-amino alcohol ligand depicting high catalytic activity and pronounced non-linear stereochemical effects
Reddy, Katamreddy Subba,Sola, Lluis,Moyano, Albert,Pericas, Miquel A.,Riera, Antoni
, p. 165 - 176 (2007/10/03)
The Jacobsen epoxidation of 9-alkylidenefluorenes 4a (ethylidene), 4b (benzylidene) and 4c (1-naphtylmethylene) with standard (R,R)-manganese salen catalyst has been studied. Both conversion and enantioselectivity depend on the steric bulk of the olefin substituent, best results being recorded with 4b (96% yield, 99% ee). The stereochemical course of the epoxidation of 4a is highly dependent on temperature and solvent, the ee of the resulting epoxide (S)-5a varying from 22% (-18°C, CH2Cl2) to 49% (55°C, MTBE). The lithium perchlorate induced ring-opening of 5a with piperidine in MeCN affords a mixture of regioisomeric amino alcohols 3a/2a arising from the amine attack at the more substituted and less substituted carbons, respectively. The 3a/2a ratio can be modulated by the LiClO4 concentration and the reaction temperature, and varies from 44:56 to 91:9. An independent, completely regiocontrolled synthesis of 3a has been developed involving ring-opening by the more substituted carbon of epoxide 5a with diisopropoxytitanium diazide, reduction of azidoalcohol 10a (H2, Pd/C) and cycloalkylation (1,5- dibromopentane, K2CO3) of the amino alcohol 11a. The amino alcohol 3a exhibits a positive nonlinear stereochemical effect in its action as a ligand for the enantioselective addition of Et2Zn to benzaldehyde. The use of regiochemically pure 3a of >99% ee has been studied in the addition of Et2Zn to a representative family of aldehydes [19 examples, 93.6% mean ee]. The use of the directly available 9:1 mixture of 3a and 2a derived from 46-47% ee 5a as a ligand system for the enantioselective addition of Et2Zn to aldehydes [8 examples, 93.1% mean ee] is also reported.
Does the reaction between fluorenone and Grignard reagents involve free fluorenone anion radicals?
Lund, Torben,Pedersen, Morten L.,Frandsen, Lars A.
, p. 9225 - 9226 (2007/10/02)
The ratio between 1,6- and 1,2-addition in the reactions of electrogenerated fluorenone anion radicals with RX in THF were similar to the ratio obtained in the Grignard reaction of fluorenone with RMgX in THF. This indicates that the addition products in the Grignard reaction may be; obtained via the coupling of Freely diffusing fluorenone anion radicals with R radicals.
REACTIVITY OF CARBANIONS. XXIII. WITTIG REARRANGEMENT OF 9-FLUORENOL ETHERS UNDER THE CONDITIONS OF PHASE-TRANSFER CATALYSIS
Solov'yanov, A. A.,El-Said, Ahmed Ali Ahmed,Beletskaya, I. P.,Reutov, O. A.
, p. 1232 - 1243 (2007/10/02)
The Wittig rearrangement of the phenyl, methyl, benzyl, and allyl ethers of 9-fluorenol was investigated under the conditions of phase-transfer catalysis in a system consisting of a solid powdered base and an organic phase.With the exception of the phenyl ether, which does not enter into the reaction, the rearrangement of all the ethers takes place by a dissociation-recombination mechanism with the formation of the fluorenone-migrating group carbanion pair as intermediate.The migratory aptitude increases in the order methyl benzyl allyl.The orders of effectiveness were established for the bases, phase transfer catalysts, and solvent in the Wittig rearrangement.
