Selective chemical reactions in supercritical carbon dioxide, water, and ionic liquids

Figures & data

Figure 1.  Chemical transformations in green solvents.

Figure 2.  Schematic phase diagram of CO₂.

short-legendScheme 1. Palladium-catalyzed coupling reaction in scCO2.

short-legendScheme 2. Synthesis of heterogeneous Pd(7)Cl2 catalyst.

short-legendScheme 3. Rhodium-catalyzed intramolecular hydroaminomethylation in scCO2.

short-legendScheme 4. Proposed mechanism of the synthesis of the pyrrolidine 9.

short-legendScheme 5. Possible mechanism of the synthesis of the bicyclic bisamino 10.

Table 1. Optimization of the hydroformylation conditions of hex-1-ene in scCO₂.

Ligand (L)	Solvent	Time (Hours)	1:2 (%)	n:i
PEt3	Toluene	1	74:4.8	2.1
PEt3	scCO2	1	82:2.3	2.4
PEt3	scCO2	2	89:8.1	2.5
PEt2Rf	scCO2	1	81:–	2.4
PEt3	scCO2/RfOH	1	82:11	2.5
Note: Rf=C6F13CH2CH2.

short-legendScheme 6. Hydroformylation of 1-octene in scCO2 using fluorinated phosphine ligands.

short-legendScheme 7. Rhodium-catalyzed hydroboration of styrene derivatives in scCO2.

short-legendScheme 8. Rhodium-catalyzed hydrogenation of alkenes in scCO2.

short-legendScheme 9. Ruthenium-catalyzed asymmetric hydrogenation of tiglic acid in scCO2.

short-legendScheme 10. Design of new chiral fluorinated phosphine ligands based on BINAP for asymmetric hydrogenation.

short-legendScheme 11. Iridium-catalyzed enantioselective hydrogenation of prochiral in scCO2.

Figure 3.  Examples of water soluble ligands.

short-legendScheme 12. Synthesis of water-soluble ligands based on triphenyl phosphine.

short-legendScheme 13. Palladium-catalyzed Heck type reaction in water.

short-legendScheme 14. Palladium-catalyzed Sonogashira type reaction in water.

short-legendScheme 15. Palladium-catalyzed benzofuranes synthesis via tandem reaction in water.

short-legendScheme 16. Palladium-catalyzed coupling of acid chloride with terminal alkynes in water.

short-legendScheme 17. Platinum-catalyzed stereoselective hydrosilylation of terminal alkynes in water.

short-legendScheme 18. Platinum-catalyzed allylation of aminonaphthalenes with allylic acetates in water.

short-legendScheme 19. Nickel-catalyzed pyrimidine derivatives synthesis in water.

short-legendScheme 20. Cobalt-catalyzed intramolecular Pauson-Khand-type reaction in water.

short-legendScheme 21. Rhodium-catalyzed enantioselective intramolecular Pauson-Khand-type reaction.

short-legendScheme 22. Rhodium-catalyzed addition of phenylboronic acid with various alkenes in water.

short-legendScheme 23. Ruthenium-catalyzed isomerization of homo-allylic alcohols and aldol-type reaction in water.

short-legendScheme 24. Ruthenium-catalyzed propargylalcohols and propargylamines in water.

short-legendScheme 25. Copper-catalyzed enantioselective addition of terminal alkynes.

short-legendScheme 26. Copper-catalyzed diastereoselective three component coupling in water.

short-legendScheme 27. Silver-catalyzed three component coupling in water.

short-legendScheme 28. Silver-catalyzed alkynylation of aldehydes and ketones in water.

short-legendScheme 29. Silver-catalyzed annulation of simple o-hydroxyaldehydes with arylalkynes.

short-legendScheme 30. Gold-catalyzed three component coupling in water.

short-legendScheme 31. Gold-catalyzed diastereoselective three component coupling in water.

short-legendScheme 32. Gold(III)-salen complexes catalyzed three component coupling in water.

short-legendScheme 33. Gold-catalyzed 1-substituted 3-aminoindolizines synthesis in water.

Figure 4.  Examples of ionic liquids (ILs).

Figure 5.  (a) Examples of ionic liquids with dual biological function; (b) Synthesis of imidazole-based RTILs from biorenewable sources.

short-legendScheme 34. Palladium-catalyzed coupling of aryl bromides with electron-rich olefins in ILs.

short-legendScheme 35. Palladium-catalyzed coupling of iodoenones with vinyl and phenyl tributyltin in ILs.

short-legendScheme 36. Palladium-carbene ligand catalyzed carbonylation of aryl halides in ILs.

short-legendScheme 37. Palladium-catalyzed tandem Knoevenagel type-reaction followed by catalytic hydrogenation in ILs.

short-legendScheme 38. Iridium-catalyzed reductive amination of carbonyl compounds with amines in ILs.

short-legendScheme 39. Iridium-catalyzed enantioselective hydrogenation of imines in ILs.

short-legendScheme 40. Rhodium-catalyzed hydroformylation of alkenes in ILs.

short-legendScheme 41. Rhodium-catalyzed intramolecular cycloisomerization of dienes with alkenes in ILs.

Table 2. Polymerization of phenylacetylene in various ILs.

ILs	Catalysis	Isolated yield (%)	Mw (Da)	Mw/Mn	Percentage of cis
[bmim]BF4	(nbd)Rh(acac)	92	196,000	4.5	98
[bupy]BF4	(nbd)Rh(acac)	91	110,000	5.6	100
[bmim]BF4	[(nbd)RhCl]	75	199,000	3.9	96
[bupy]BF4	[(nbd)RhCl]	63	120,000	8.5	99
Notes: PPA, poly(phenylacetylene); nbd, norbornadiene; acac, acetylacetone.

short-legendScheme 42. Rhodium-catalyzed tandem cyclization-1,3-dipolar cycloaddition reaction of α-diazo ketones in ILs.

short-legendScheme 43. Ruthenium-catalyzed enantioselective hydrogenation of ketone and derivatives in ILs.

Table 3. Comparative recycling and reuse of Ru-based catalysts for RCM in ILs.

	Cycle (percentage of conversion)^a
Catalysis	1	2	3	4	5	6	7	8	9
A	>98	>98	>98	>98	>98	96	92	92	92
B	>98	40	20	–	–	–	–	–	–
C	>98	20	–	–	–	–	–	–	–
^aDetermined by ^1H NMR.

short-legendScheme 44. Ruthenium-catalyzed Aldol and Mannich-type reactions in ILs.

Table 4. Cyclooligomerization of arylethynes in ILs.

		Yield (%)
Ils	R	146	147	148
[bmim][PF6]	H	32	17	30
[omim][PF6]	H	60	6	9
[bmim][PF6]	OMe	21	–	–
[omim][PF6]	OMe	67	–	–
Note: Ru(TPP)CO: 5,10,15,20-tetraphenylporphyrinatoruthenium(II) carbonyl; [bmim][PF6]: 1-butyl-3-methylimidazolium hexafluorophosphate; and [omim][PF6]: 1-octyl-3-methylimidazolium hexafluorophosphate.

short-legendScheme 45. Copper-catalyzed selective oxidation of alcohols in ILs.

short-legendScheme 46. Copper-catalyzed azide-alkyne click reaction in ILs.

Table 5. Comparative study of Diels–Alder reaction in ILs and dichloromethane.

L	Solvent	Time (Min)	Conversion (%)	Endo ee	Percentage of endo
L 1	[emim][PF6]	2	100	84	88
L 1	CH2CL2	60	43	12	86
L 2	[emim][PF6]	2	100	95	90
L 2	CH2CL2	60	78	78	88