甲烷均相转化研究进展
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摘要
在绿色、经济的反应条件下实现甲烷的直接转化一直是化工能源领域面临的重大挑战之一.在过去的10年中,有机合成化学家们相继发展了多种甲烷均相转化方法,为利用丰富的甲烷作为化工原料来合成高附加值的化工产品提供了新的转化途径.本文从反应作用机制方面总结了近年来甲烷均相转化领域的研究进展,包括过渡金属和主族金属参与的,以及光促进的甲烷均相转化等.在这些研究进展中,过渡金属催化的甲烷转化方法占据主要,涌现了对甲烷碳氢键进行亲电活化、氧化加成和卡宾插入等多种不同活化机制.引人注意的是,光催化模式利用清洁的光能为反应提供能量,为甲烷的均相转化提供了一种更加绿色可持续的化学转化方案.文末对发展更多高效的光促甲烷转化反应及其应用前景进行了展望.
Methane is one of the most abundant and inexpensive carbon-based feedstocks on earth. It is the major component of natural gas, which is considered as a greener fuel and promising alternative to petroleum for energy and chemicals production. However, the prevalent methane utilization was largely limited by its chemical properties and existing processes for methane upgrading. On one side, the low boiling point of methane(109 K at 1 atm), rendered the liquefaction of methane for long-distance transportation economically impractical. On the other side, the direct conversion of methane to value-added liquid chemicals is rewarding, but challenging processes due to its inert chemical properties, namely, high bond dissociation energy(～105 kcal/mol), ionization potential(12.6 eV), relatively low solubility in solvents. Moreover,the functionalized products(e.g., methanol, acetic acid) and the solvents(e.g., hexane, acetonitrile) show the higher reactivities than methane, resulting the selectivity issues, such as the overfunctionalizations and solvent activations.Accordingly, the development of efficient selective processes to directly convert methane into value-added liquid products under economical and green reaction conditions has been of significant importance and remains one of the grand challenges in synthetic chemistry.In the 20 th century, considerable efforts have been devoted to the selective oxidation of methane to methanol and methanol derivatives. In the initial stage, the processes were dominated by energy intensive systems with harsh reaction conditions, such as high temperature, high pressure and high catalyst loading. Therefore, new catalytic modes have been highly demanding for the sake of more sustainable and affordable methane conversion process. During the last decade, a variety of direct C–H functionalizations of methane has been achieved in the realm of synthetic organic chemistry.Nevertheless, in comparison to the advancement in heterogeneous functionalization of methane, the homogenous approach remains relatively underdeveloped, thusly intriguing opportunities lies therein.The recent advancement of transition metal homogenous catalysis has greatly facilitated the direct activation of those symmetric C–H bonds of methane. Amongst the reported transformations, strategies including electrophilic activation,carbene insertion and oxidative addition have been frequently employed in homogeneous functionalizations of methane. In some cases, main-group metals could also function in a similar pathway. Notably, photocatalysis that can directly utilize light energy for chemical activation, has also been applied in the homogenous functionalization of methane. As reactions largely proceed by free radicals, the intermolecular hydrogen atom transfer process should be the crucial step in this catalytic pattern. Pleasingly, the mild reaction conditions and high selectivity of these photo-induced functionalizations have paved a way for developing more cost-effective and environmentally benign functionalizations of methane.Herein, we aim to highlight the recent advance in homogeneous functionalizations of methane, in particular, underline the novel transition metal catalytic and photocatalytic manifolds that we would anticipate spur more brilliant studies towards the versatile functionalizations of methane. The context was thus arranged in three parts according to the mechanism of homogenous functionalization endeavors, including the transition metal catalyzed methane activation, maingroup metals mediated electrophilic activation of methane and photocatalytic functionalizations of methane. We believe this classification of existing literatures would shed some light on the future progress in homogenous functionalizations of methane.
Methane is one of the most abundant and inexpensive carbon-based feedstocks on earth. It is the major component of natural gas, which is considered as a greener fuel and promising alternative to petroleum for energy and chemicals production. However, the prevalent methane utilization was largely limited by its chemical properties and existing processes for methane upgrading. On one side, the low boiling point of methane(109 K at 1 atm), rendered the liquefaction of methane for long-distance transportation economically impractical. On the other side, the direct conversion of methane to value-added liquid chemicals is rewarding, but challenging processes due to its inert chemical properties, namely, high bond dissociation energy(～105 kcal/mol), ionization potential(12.6 eV), relatively low solubility in solvents. Moreover,the functionalized products(e.g., methanol, acetic acid) and the solvents(e.g., hexane, acetonitrile) show the higher reactivities than methane, resulting the selectivity issues, such as the overfunctionalizations and solvent activations.Accordingly, the development of efficient selective processes to directly convert methane into value-added liquid products under economical and green reaction conditions has been of significant importance and remains one of the grand challenges in synthetic chemistry.In the 20 th century, considerable efforts have been devoted to the selective oxidation of methane to methanol and methanol derivatives. In the initial stage, the processes were dominated by energy intensive systems with harsh reaction conditions, such as high temperature, high pressure and high catalyst loading. Therefore, new catalytic modes have been highly demanding for the sake of more sustainable and affordable methane conversion process. During the last decade, a variety of direct C–H functionalizations of methane has been achieved in the realm of synthetic organic chemistry.Nevertheless, in comparison to the advancement in heterogeneous functionalization of methane, the homogenous approach remains relatively underdeveloped, thusly intriguing opportunities lies therein.The recent advancement of transition metal homogenous catalysis has greatly facilitated the direct activation of those symmetric C–H bonds of methane. Amongst the reported transformations, strategies including electrophilic activation,carbene insertion and oxidative addition have been frequently employed in homogeneous functionalizations of methane. In some cases, main-group metals could also function in a similar pathway. Notably, photocatalysis that can directly utilize light energy for chemical activation, has also been applied in the homogenous functionalization of methane. As reactions largely proceed by free radicals, the intermolecular hydrogen atom transfer process should be the crucial step in this catalytic pattern. Pleasingly, the mild reaction conditions and high selectivity of these photo-induced functionalizations have paved a way for developing more cost-effective and environmentally benign functionalizations of methane.Herein, we aim to highlight the recent advance in homogeneous functionalizations of methane, in particular, underline the novel transition metal catalytic and photocatalytic manifolds that we would anticipate spur more brilliant studies towards the versatile functionalizations of methane. The context was thus arranged in three parts according to the mechanism of homogenous functionalization endeavors, including the transition metal catalyzed methane activation, maingroup metals mediated electrophilic activation of methane and photocatalytic functionalizations of methane. We believe this classification of existing literatures would shed some light on the future progress in homogenous functionalizations of methane.
引文
1 Schwach P,Pan X,Bao X.Direct conversion of methane to value-added chemicals over heterogeneous catalysts:Challenges and prospects.Chem Rev,2017,117:8497-8520
2 Crabtree R H.Aspects of methane chemistry.Chem Rev,1995,95:987-1007
3 Cavaliere V N,Wicker B F,Mindiola D J.Homogeneous organometallic chemistry of methane.Adv Organomet Chem,2012,60:1-47
4 Caballero A,Pérez P J.Methane as raw material in synthetic chemistry:The final frontier.Chem Soc Rev,2013,42:8809-8820
5 Gunsalus N J,Koppaka A,Park S H,et al.Homogeneous functionalization of methane.Chem Rev,2017,117:8521-8573
6 Shilov A E,Shteinman A A.Activation of saturated hydrocarbons by metal complexes in solution.Coord Chem Rev,1977,24:97-143
7 Shilov A E,Shul’pin G B.Activation of C-H bonds by metal complexes.Chem Rev,1997,97:2879-2932
8 Periana R A,Taube D J,Gamble S,et al.Platinum catalysts for the high-yield oxidation of methane to a methanol derivative.Science,1998,280:560-564
9 Mironov O A,Bischof S M,Konnick M M,et al.Using reduced catalysts for oxidation reactions:Mechanistic studies of the“periana-catalytica”system for CH4oxidation.J Am Chem Soc,2013,135:14644-14658
10 Soorholtz M,White R J,Zimmermann T,et al.Direct methane oxidation over Pt-modified nitrogen-doped carbons.Chem Commun,2013,49:240-242
11 Zimmermann T,Bilke M,Soorholtz M,et al.Influence of catalyst concentration on activity and selectivity in selective methane oxidation with platinum compounds in sulfuric acid and oleum.ACS Catal,2018,8:9262-9268
12 Zimmermann T,Soorholtz M,Bilke M,et al.Selective methane oxidation catalyzed by platinum salts in oleum at turnover frequencies of largescale industrial processes.J Am Chem Soc,2016,138:12395-12400
13 An Z,Pan X,Liu X,et al.Combined redox couples for catalytic oxidation of methane by dioxygen at low temperatures.J Am Chem Soc,2006,128:16028-16029
14 Duester G.Involvement of alcohol dehydrogenase,short-chain dehydrogenase/reductase,aldehyde dehydrogenase,and cytochrome P450 in the control of retinoid signaling by activation of retinoic acid synthesis.Biochemistry,1996,35:12221-12227
15 Yuan J,Liu L,Wang L,et al.Partial oxidation of methane with the catalysis of palladium(II)and molybdovanadophosphoric acid using molecular oxygen as the oxidant.Catal Lett,2013,143:126-129
16 Yuan J,Wang Y,Hao C.Water-promoted palladium catalysts for methane oxidation.Catal Lett,2013,143:610-615
17 Meyer D,Zeller A,Strassner T.Platinum complexes with pyrimidine-functionalized N-heterocyclic carbene ligands-Synthesis and solid state structures.J Organomet Chem,2012,701:56-61
18 Munz D,Meyer D,Strassner T.Methane CH activation by palladium complexes with chelating bis(NHC)ligands:A DFT study.Organometallics,2013,32:3469-3480
19 Meyer D,Strassner T.CH-activation of methane-Synthesis of an intermediate?J Organomet Chem,2015,784:84-87
20 Strassner T,Ahrens S,Muehlhofer M,et al.Cobalt-catalyzed oxidation of methane to methyl trifluoroacetate by dioxygen.Eur J Inorg Chem,2013,(21):3659-3663
21 Lanci M P,Remy M S,Kaminsky W,et al.Oxidatively induced reductive elimination from(tBu2bpy)Pd(Me)2:Palladium(IV)intermediates in a one-electron oxidation reaction.J Am Chem Soc,2009,131:15618-15620
22 Remy M S,Cundari T R,Sanford M S.Computational and experimental studies of methyl group exchange between palladium(ii)centers.Organometallics,2010,29:1522-1525
23 Lotz M D,Remy M S,Lao D B,et al.Formation of ethane from mono-methyl palladium(II)complexes.J Am Chem Soc,2014,136:8237-8242
24 Li Q,Liskey C W,Hartwig J F.Regioselective borylation of the C-H bonds in alkylamines and alkyl ethers:Observation and origin of high reactivity of primary C-H bonds beta to nitrogen and oxygen.J Am Chem Soc,2014,136:8755-8765
25 Hartwig J F,Cook K S,Hapke M,et al.Rhodium boryl complexes in the catalytic,terminal functionalization of alkanes.J Am Chem Soc,2005,127:2538-2552
26 Liskey C W,Hartwig J F.Iridium-catalyzed borylation of secondary C-H bonds in cyclic ethers.J Am Chem Soc,2012,134:12422-12425
27 Wei C S,Jimenez-Hoyos C A,Videa M F,et al.Origins of the selectivity for borylation of primary over secondary C-H bonds catalyzed by Cp*-rhodium complexes.J Am Chem Soc,2010,132:3078-3091
28 Cook A K,Schimler S D,Matzger A J,et al.Catalyst-controlled selectivity in the C-H borylation of methane and ethane.Science,2016,351:1421-1424
29 Smith K T,Berritt S,González-Moreiras M,et al.Catalytic borylation of methane.Science,2016,351:1424-1427
30 Ahn S,Sorsche D,Berritt S,et al.Rational design of a catalyst for the selective monoborylation of methane.ACS Catal,2018,8:10021-10031
31 Carlsen R,Wohlgemuth N,Carlson L,et al.Dynamical mechanism may avoid high-oxidation state Ir(V)-H intermediate and coordination complex in alkane and arene C-H activation by cationic Ir(III)phosphine.J Am Chem Soc,2018,140:11039-11045
32 Caballero A,Despagnet-Ayoub E,Mar Diaz-Requejo M,et al.Silver-catalyzed C-C bond formation between methane and ethyl diazoacetate in supercritical CO2.Science,2011,332:835-838
33 Fuentes Má,Olmos A,Mu?oz B K,et al.Catalytic functionalization of methane and light alkanes in supercritical carbon dioxide.Chem Eur J,2014,20:11013-11018
34 Olmos A,Gava R,Noverges B,et al.Measuring the relative reactivity of the carbon-hydrogen bonds of alkanes as nucleophiles.Angew Chem Int Ed,2018,57:13848-13852
35 Gava R,Olmos A,Noverges B,et al.Discovering copper for methane C-H bond functionalization.ACS Catal,2015,5:3726-3730
36 Hashiguchi B G,Konnick M M,Bischof S M,et al.Main-group compounds selectively oxidize mixtures of methane,ethane,and propane to alcohol esters.Science,2014,343:1232-1237
37 Ohkubo K,Hirose K.Light-driven C-H oxygenation of methane into methanol and formic acid by molecular oxygen using a perfluorinated solvent.Angew Chem Int Ed,2018,57:2126-2129
38 Hu A,Guo J J,Pan H,et al.Selective functionalization of methane,ethane,and higher alkanes by cerium photocatalysis.Science,2018,361:668-672
39 Guo J J,Hu A,Chen Y,et al.Photocatalytic C-C bond cleavage and amination of cycloalkanols by cerium(III)chloride complex.Angew Chem Int Ed,2016,55:15319-15322
40 Hu A,Guo J J,Pan H,et al.δ-Selective functionalization of alkanols enabled by visible-light-induced ligand-to-metal charge transfer.J Am Chem Soc,2018,140:1612-1616
41 Guo J J,Hu A,Zuo Z.Photocatalytic alkoxy radical-mediated transformations.Tetrahedron Lett,2018,59:2103-2111
42 Hu A,Chen Y,Guo J J,et al.Cerium-catalyzed formal cycloaddition of cycloalkanols with alkenes through dual photoexcitation.J Am Chem Soc,2018,140:13580-13585
43 Twilton J,Le C C,Zhang P,et al.The merger of transition metal and photocatalysis.Nat Rev Chem,2017,1:0052
44 Wang F,Stahl S S.Merging photochemistry with electrochemistry:Functional group tolerant electrochemical amination of sp3C-H bonds.Angew Chem Int Ed,2019,58:1-7
45 Yan M,Kawamata Y,Baran P S.Synthetic organic electrochemical methods since 2000:On the verge of a renaissance.Chem Rev,2000,117:13230-13319
46 Tang S,Liu Y,Lei A.Electrochemical oxidative cross-coupling with hydrogen evolution:A green and sustainable way for bond formation.Chem,2018,4:27-45
47 Ma C,Fang P,Mei T S.Recent advances in C-H functionalization using electrochemical transition metal catalysis.ACS Catal,2018,8:7179-7189
48 Yang Q L,Li Y Q,Ma C,et al.Palladium-catalyzed C(sp3)-H oxygenation via electrochemical oxidation.J Am Chem Soc,2017,139:3293-3298
49 O’Reilly M E,Kim R S,Oh S,et al.Catalytic methane monofunctionalization by an electrogenerated high-valent Pd intermediate.ACS Cent Sci,2017,3:1174-1179
2 Crabtree R H.Aspects of methane chemistry.Chem Rev,1995,95:987-1007
3 Cavaliere V N,Wicker B F,Mindiola D J.Homogeneous organometallic chemistry of methane.Adv Organomet Chem,2012,60:1-47
4 Caballero A,Pérez P J.Methane as raw material in synthetic chemistry:The final frontier.Chem Soc Rev,2013,42:8809-8820
5 Gunsalus N J,Koppaka A,Park S H,et al.Homogeneous functionalization of methane.Chem Rev,2017,117:8521-8573
6 Shilov A E,Shteinman A A.Activation of saturated hydrocarbons by metal complexes in solution.Coord Chem Rev,1977,24:97-143
7 Shilov A E,Shul’pin G B.Activation of C-H bonds by metal complexes.Chem Rev,1997,97:2879-2932
8 Periana R A,Taube D J,Gamble S,et al.Platinum catalysts for the high-yield oxidation of methane to a methanol derivative.Science,1998,280:560-564
9 Mironov O A,Bischof S M,Konnick M M,et al.Using reduced catalysts for oxidation reactions:Mechanistic studies of the“periana-catalytica”system for CH4oxidation.J Am Chem Soc,2013,135:14644-14658
10 Soorholtz M,White R J,Zimmermann T,et al.Direct methane oxidation over Pt-modified nitrogen-doped carbons.Chem Commun,2013,49:240-242
11 Zimmermann T,Bilke M,Soorholtz M,et al.Influence of catalyst concentration on activity and selectivity in selective methane oxidation with platinum compounds in sulfuric acid and oleum.ACS Catal,2018,8:9262-9268
12 Zimmermann T,Soorholtz M,Bilke M,et al.Selective methane oxidation catalyzed by platinum salts in oleum at turnover frequencies of largescale industrial processes.J Am Chem Soc,2016,138:12395-12400
13 An Z,Pan X,Liu X,et al.Combined redox couples for catalytic oxidation of methane by dioxygen at low temperatures.J Am Chem Soc,2006,128:16028-16029
14 Duester G.Involvement of alcohol dehydrogenase,short-chain dehydrogenase/reductase,aldehyde dehydrogenase,and cytochrome P450 in the control of retinoid signaling by activation of retinoic acid synthesis.Biochemistry,1996,35:12221-12227
15 Yuan J,Liu L,Wang L,et al.Partial oxidation of methane with the catalysis of palladium(II)and molybdovanadophosphoric acid using molecular oxygen as the oxidant.Catal Lett,2013,143:126-129
16 Yuan J,Wang Y,Hao C.Water-promoted palladium catalysts for methane oxidation.Catal Lett,2013,143:610-615
17 Meyer D,Zeller A,Strassner T.Platinum complexes with pyrimidine-functionalized N-heterocyclic carbene ligands-Synthesis and solid state structures.J Organomet Chem,2012,701:56-61
18 Munz D,Meyer D,Strassner T.Methane CH activation by palladium complexes with chelating bis(NHC)ligands:A DFT study.Organometallics,2013,32:3469-3480
19 Meyer D,Strassner T.CH-activation of methane-Synthesis of an intermediate?J Organomet Chem,2015,784:84-87
20 Strassner T,Ahrens S,Muehlhofer M,et al.Cobalt-catalyzed oxidation of methane to methyl trifluoroacetate by dioxygen.Eur J Inorg Chem,2013,(21):3659-3663
21 Lanci M P,Remy M S,Kaminsky W,et al.Oxidatively induced reductive elimination from(tBu2bpy)Pd(Me)2:Palladium(IV)intermediates in a one-electron oxidation reaction.J Am Chem Soc,2009,131:15618-15620
22 Remy M S,Cundari T R,Sanford M S.Computational and experimental studies of methyl group exchange between palladium(ii)centers.Organometallics,2010,29:1522-1525
23 Lotz M D,Remy M S,Lao D B,et al.Formation of ethane from mono-methyl palladium(II)complexes.J Am Chem Soc,2014,136:8237-8242
24 Li Q,Liskey C W,Hartwig J F.Regioselective borylation of the C-H bonds in alkylamines and alkyl ethers:Observation and origin of high reactivity of primary C-H bonds beta to nitrogen and oxygen.J Am Chem Soc,2014,136:8755-8765
25 Hartwig J F,Cook K S,Hapke M,et al.Rhodium boryl complexes in the catalytic,terminal functionalization of alkanes.J Am Chem Soc,2005,127:2538-2552
26 Liskey C W,Hartwig J F.Iridium-catalyzed borylation of secondary C-H bonds in cyclic ethers.J Am Chem Soc,2012,134:12422-12425
27 Wei C S,Jimenez-Hoyos C A,Videa M F,et al.Origins of the selectivity for borylation of primary over secondary C-H bonds catalyzed by Cp*-rhodium complexes.J Am Chem Soc,2010,132:3078-3091
28 Cook A K,Schimler S D,Matzger A J,et al.Catalyst-controlled selectivity in the C-H borylation of methane and ethane.Science,2016,351:1421-1424
29 Smith K T,Berritt S,González-Moreiras M,et al.Catalytic borylation of methane.Science,2016,351:1424-1427
30 Ahn S,Sorsche D,Berritt S,et al.Rational design of a catalyst for the selective monoborylation of methane.ACS Catal,2018,8:10021-10031
31 Carlsen R,Wohlgemuth N,Carlson L,et al.Dynamical mechanism may avoid high-oxidation state Ir(V)-H intermediate and coordination complex in alkane and arene C-H activation by cationic Ir(III)phosphine.J Am Chem Soc,2018,140:11039-11045
32 Caballero A,Despagnet-Ayoub E,Mar Diaz-Requejo M,et al.Silver-catalyzed C-C bond formation between methane and ethyl diazoacetate in supercritical CO2.Science,2011,332:835-838
33 Fuentes Má,Olmos A,Mu?oz B K,et al.Catalytic functionalization of methane and light alkanes in supercritical carbon dioxide.Chem Eur J,2014,20:11013-11018
34 Olmos A,Gava R,Noverges B,et al.Measuring the relative reactivity of the carbon-hydrogen bonds of alkanes as nucleophiles.Angew Chem Int Ed,2018,57:13848-13852
35 Gava R,Olmos A,Noverges B,et al.Discovering copper for methane C-H bond functionalization.ACS Catal,2015,5:3726-3730
36 Hashiguchi B G,Konnick M M,Bischof S M,et al.Main-group compounds selectively oxidize mixtures of methane,ethane,and propane to alcohol esters.Science,2014,343:1232-1237
37 Ohkubo K,Hirose K.Light-driven C-H oxygenation of methane into methanol and formic acid by molecular oxygen using a perfluorinated solvent.Angew Chem Int Ed,2018,57:2126-2129
38 Hu A,Guo J J,Pan H,et al.Selective functionalization of methane,ethane,and higher alkanes by cerium photocatalysis.Science,2018,361:668-672
39 Guo J J,Hu A,Chen Y,et al.Photocatalytic C-C bond cleavage and amination of cycloalkanols by cerium(III)chloride complex.Angew Chem Int Ed,2016,55:15319-15322
40 Hu A,Guo J J,Pan H,et al.δ-Selective functionalization of alkanols enabled by visible-light-induced ligand-to-metal charge transfer.J Am Chem Soc,2018,140:1612-1616
41 Guo J J,Hu A,Zuo Z.Photocatalytic alkoxy radical-mediated transformations.Tetrahedron Lett,2018,59:2103-2111
42 Hu A,Chen Y,Guo J J,et al.Cerium-catalyzed formal cycloaddition of cycloalkanols with alkenes through dual photoexcitation.J Am Chem Soc,2018,140:13580-13585
43 Twilton J,Le C C,Zhang P,et al.The merger of transition metal and photocatalysis.Nat Rev Chem,2017,1:0052
44 Wang F,Stahl S S.Merging photochemistry with electrochemistry:Functional group tolerant electrochemical amination of sp3C-H bonds.Angew Chem Int Ed,2019,58:1-7
45 Yan M,Kawamata Y,Baran P S.Synthetic organic electrochemical methods since 2000:On the verge of a renaissance.Chem Rev,2000,117:13230-13319
46 Tang S,Liu Y,Lei A.Electrochemical oxidative cross-coupling with hydrogen evolution:A green and sustainable way for bond formation.Chem,2018,4:27-45
47 Ma C,Fang P,Mei T S.Recent advances in C-H functionalization using electrochemical transition metal catalysis.ACS Catal,2018,8:7179-7189
48 Yang Q L,Li Y Q,Ma C,et al.Palladium-catalyzed C(sp3)-H oxygenation via electrochemical oxidation.J Am Chem Soc,2017,139:3293-3298
49 O’Reilly M E,Kim R S,Oh S,et al.Catalytic methane monofunctionalization by an electrogenerated high-valent Pd intermediate.ACS Cent Sci,2017,3:1174-1179