Aqueous Ti(IV)-Catalyzed Diels-Alder Reaction

Litz, Kyle E.

doi:10.3390/12081674

Cited by 9 publications

(5 citation statements)

References 7 publications

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“…68,69 Other Lewis acids that are air stable and water tolerant have also been reported for the Diels-Alder reaction of furan with suitable dienophiles. [70][71][72] The above highlight can be said to have established the platform for the application of Diels-Alder reactions for the formation of C 12 -biofuel intermediates exclusively from HMF. A C 12 or C 10 biofuel intermediate can be formed via the hetero Diels-Alder condensation of two HMF or furfural molecules respectively with a furan ring as the diene and the carbonyl group as the dienophile.…”

Section: Cross-condensation Of Hmf (Non C-c Coupling)mentioning

confidence: 99%

Towards the conversion of carbohydrate biomass feedstocks to biofuels via hydroxylmethylfurfural

James

Maity

Usman

et al. 2010

Energy Environ. Sci.

184

109

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This review appraises the chemical conversion processes recently reported for the production of hydroxylmethylfurfural (HMF), a key biorefining intermediate, from carbohydrate biomass feedstocks. Catalytic sites or groups required for the efficient and selective conversion of hexose substrates to HMF are examined. The principle of concerted catalysis was used to rationalise the dehydration of fructose and glucose to HMF in non-aqueous media. A survey of reported reaction routes to diesel-range biofuel intermediates from HMF or furfural is presented and self-condensation reaction routes for linking two or more HMF and furfural units together toward obtaining kerosene and diesel-range biofuel intermediates are highlighted. The reaction routes include: benzoin condensation, condensation of furfuryl alcohols, hetero Diels-Alder reaction and ketonisation reaction. These reaction routes are yet to be exploited despite their potential for obtaining kerosene and diesel-range biofuel intermediates exclusively from furfural or hydroxylmethylfurfural.

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Section: Cross-condensation Of Hmf (Non C-c Coupling)mentioning

confidence: 99%

Towards the conversion of carbohydrate biomass feedstocks to biofuels via hydroxylmethylfurfural

James

Maity

Usman

et al. 2010

Energy Environ. Sci.

184

109

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“…Still, water promoted better reaction yields than the organic solvent (toluene) did as illustrated in Table 3. In the case of the cyclohexa-1,3-diene 16, the yield and the reaction time were improved to 83% and 20 h, respectively, by using Ti(IV) Lewis acid as a catalyst [47]. The occurrence of a hydrophobic packing of the diene and the dienophile in the transition state would account for the greater yields of water-promoted DA reactions, particularly in the case of 16.…”

Section: [ ( S C H E M E _ 2 ) T D $ F I G ]mentioning

confidence: 99%

Cycloaddition reactions in aqueous systems: A two-decade trend endeavor

Moulay

Touati

2010

Comptes Rendus. Chimie

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Cycloaddition reactions are an integral and weighty part of organic chemistry in pedagogy and research as well. The wealthy literature on cycloaddition reactions from their birth up to now, unequivocally witnesses to their leading chemistry. The so-called ''conventional solvents'' are organic solvents that have indubitably promoted their success. Yet, the toxicity facet of these solvents impedes their use freely and with no fear. Not only is the operating chemist uncomfortable while experimenting, but also the environment is equally threatened. Working out the cycloaddition reactions and other organic ones in aqueous systems would certainly bring some relief to the chemist and to the environment as well. Unusual outcomes in terms of yield, reactivity and selectivity compared to those performed in organic solvents were commonly observed, and have overwhelmed the chemists with surprise indeed. In this review, homo Diels-Alder reactions in aqueous media include those involving the following dienophiles: maleimides, a,b-unsaturated esters, p-benzoquinones, vinyl ketones, phenyl-1-(2-pyridyl)-2-propen-1-one, a,bunsaturated esters. A special case is the organocatalysis of Diels-Alder cycloaddition of a,b-unsaturated ketones (aldehydes). Of no less importance, some hetero Diels-Alder cycloaddition reactions in water systems are delineated. The impact of additives (salts, organic and inorganic chemicals), micellar catalysis and Lewis/Brønste ¨d acid catalysis on outcomes of such cycloaddition reactions is discussed. The 1,3-dipolar cycloaddition methodology applied to aqueous media has brought forth a number of heterocyclic compounds, usually with a regio-and stereoselectivity pecularity. These heterocycles include triazoles, tetrazoles, pyrazoles, isoxazoles, isoxazolidines, pyrroles and pyrrolidines. The superiority of copper(I) catalysis in the azide-alkyne cycloaddition (Huisgen cycloaddition) in water is endorsed by a number of examples.

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“…Titanium with its highest oxidation state (+IV) is thermodynamically preferred and possesses a high electrostatic potential and therefore exhibits high Lewis acidity [8] . Owing to these properties, titanium compounds have been reported to exhibit exceptional reactivity towards various organic reactions such as Sharpless epoxidations, [9] olefin metathesis, [10] olefinations of carbonyl compounds, [11] Ziegler‐Natta catalysis, [12] condensation reactions, [13] Friedel‐Crafts reactions [14] and Diels‐Alder additions, [15] etc., and toward bond activation reactions like radical reactions, [16] reductive couplings, [17] and stoichiometric dinitrogen activations [18] . However, the oxophillic and moisture‐sensitive nature of titanium complexes limits its potential use as a catalyst for the synthesis of fine chemicals, pharmaceuticals, and agrochemicals in comparison to late transition metal catalysts [19] .…”

Section: Introductionmentioning

confidence: 99%

Efficient Hydroboration of Esters and Nitriles Using a Quinazolinone‐Supported Titanium(IV) Multitasking Catalyst

et al. 2023

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We report catalytic hydroboration of esters as well as nitriles under solvent‐free and mild conditions using single titanium(IV) metal complex, [{κ2‐C6H4C(O)N(iPr)C(N‐iPr)=N}{κ3‐(iPr)N=C(O)−C6H4−NC(NMe2)N(iPr)}TiNMe2] 1 as a sustainable, economical, and efficient pre‐catalyst. The molecular structure of the TiIV complex in the solid state reveals the unique coordination of TiIV metal with N, N, and O atoms of one quinazolinone unit via in‐situ rearrangement, while another quinazolinone moiety coordinates in bidentate fashion via both N atoms only. The TiIV complex demonstrates excellent activity as a pre‐catalyst towards the hydroboration of a wide array of esters and nitriles with pinacolborane (HBpin) to afford alkoxyboranes and diboryl amines in high yield (up to 99 %) with greater tolerance to a variety of electron‐withdrawing and electron‐donating functional groups. A most plausible mechanism of hydroboration of esters is also proposed based on kinetics and NMR studies, which suggests the formation of titanium‐hydride species as an active catalyst.

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Aqueous Ti(IV)-Catalyzed Diels-Alder Reaction

Cited by 9 publications

References 7 publications

Towards the conversion of carbohydrate biomass feedstocks to biofuels via hydroxylmethylfurfural

Towards the conversion of carbohydrate biomass feedstocks to biofuels via hydroxylmethylfurfural

Cycloaddition reactions in aqueous systems: A two-decade trend endeavor

Efficient Hydroboration of Esters and Nitriles Using a Quinazolinone‐Supported Titanium(IV) Multitasking Catalyst

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