Enantioselective Copper-Catalyzed Synthesis of Trifluoromethyl-Cyclopropylboronates

Abstract

A copper-catalyzed enantioselective cyclopropanation involving trifluorodiazoethane in the presence of alkenyl boronates has been developed. This transformation enables the preparation of 2-substituted-3-(trifluoromethyl)cyclopropylboronates with high levels of stereocontrol. The products are valuable synthetic intermediates by transformation of the boronate group. This methodology can be applied to the synthesis of novel trifluoromethylated analogues of trans -2-arylcyclopropylamines, which are prevalent motifs in biologically active compounds.

Transition‐Metal‐Catalyzed Reactions Involving Trifluoro Diazo Compounds and Their Surrogates

“…Further investigation of the cyclopropanation reaction was also examined under heterogeneous conditions with metalloporphyrin polymers 7 and 8, which were also efficient to give trifluoromethylphenyl cyclopropanes with high diastereoselectivity. The application of this trifluoromethyl-cyclopropanation of diverse classes of alkenes with 2,2,2-trifluorodiazoethane was extended under the rhodium, [12] copper [13] and iron catalysis, [14] a wide range of trifluoromethylsubstituted cyclopropanes, such as CF 3 -substituted 3,4-and 4,5- methanoproline analogues as 19 F NMR labels for peptides in the polyproline II conformation, CF 3 -substituted 3azabicyclo[n.1.0]alkanes, functionalized CF 3 -substituted cyclopropyltrifluoroborates, as well as CF 3 -substituted spirocyclic βlactams were afforded efficiently and simply. [15] In general, reactions of terminal alkynes with diazo compounds lead to cyclopropenation or C sp -H insertion.The reaction course strongly depends on the nature of the metal and the catalyst structure.…”

Recent Advances in Non-Precious Metal Catalysis

“…The use of a bulky and electron-rich diazonium salt was crucial to achieve efficient iodine activation, presumably due to the enhanced stability of the aryl radical. Other notable advances in Cu-catalyzed reactions include the following publications: (1) Cu-catalyzed diazidation reactions; 54 (2) Diastereo-and enantioselective oxidative 1,6conjugate addition; 55 (3) C−H amination of 8-aminoquinoline-directed ferrocenes; 56 (4) Cu-catalyzed hydroxymethylation of alkynes with formic acid; 57 (5) Cu-catalyzed synthesis of indolyl benzo[b]carbazoles; 58 (6) Cu-catalyzed tandem cross-coupling and alkynylogous aldol reaction to access exocyclic α-allenols; 59 (7) Tandem Cu-and Rh-catalysis for oxidation of hydrazones and enantioselective cyclopropanation; 60 (8) Cu-catalyzed CF 2 H-substituted 2-amidofurans; 61 (9) Cu-catalyzed annulation of indolyl α-diazocarbonyl to access carbazoles; 62 (10) Cu-catalyzed enantioselective 1,2reduction of cycloalkenones; 63 (11) Cu-catalyzed enantiodivergent alkynylation of isatins; 64 (12) Cu-catalyzed β-lactam formation from oximes and methyl propiolate; 65 (13) Cucatalyzed aminosulfonylation of O-homoallyl benzimidates; 66 (14) Cu-catalyzed multicomponent trifluoromethylphosphorothiolation of alkenes; 67 (15) Cu-catalyzed chloroarylsulfonylation of styrene derivatives; 68 (16) Cu-catalyzed synthesis of 5-carboxyl-4-perfluoroalkyl triazoles; 69 (17) Crossnucleophile coupling of β-allenyl silanes with tertiary C−H bonds to access 1,3-dienes; 70 (18) Cu-catalyzed C(sp 3 )−H functionalization of O-pentafluorobenzoyl ketone oximes; 71 (19) Total regioselectivity of hydrobromination of alkenes controlled by Fe or Cu catalyst; 72 (20) Enantioselective synthesis of trifluoromethyl cyclopropylboronates by Cu catalysis; 73 (21) Cu-catalyzed asymmetric cyclization of alkenyl diynes; 74 (22) Synergistic Ir/Cu catalysis for asymmetric allylic alkylation of oxindoles; 75…”

“…Other notable advances in Cu-catalyzed reactions include the following publications: (1) Cu-catalyzed diazidation reactions; (2) Diastereo-and enantioselective oxidative 1,6-conjugate addition; (3) C–H amination of 8-aminoquinoline-directed ferrocenes; (4) Cu-catalyzed hydroxymethylation of alkynes with formic acid; (5) Cu-catalyzed synthesis of indolyl benzo­[ b ]­carbazoles; (6) Cu-catalyzed tandem cross-coupling and alkynylogous aldol reaction to access exocyclic α-allenols; (7) Tandem Cu- and Rh-catalysis for oxidation of hydrazones and enantioselective cyclopropanation; (8) Cu-catalyzed CF 2 H-substituted 2-amidofurans; (9) Cu-catalyzed annulation of indolyl α-diazocarbonyl to access carbazoles; (10) Cu-catalyzed enantioselective 1,2-reduction of cycloalkenones; (11) Cu-catalyzed enantiodivergent alkynylation of isatins; (12) Cu-catalyzed β-lactam formation from oximes and methyl propiolate; (13) Cu-catalyzed aminosulfonylation of O -homoallyl benzimidates; (14) Cu-catalyzed multicomponent trifluoromethyl­phosphorothiolation of alkenes; (15) Cu-catalyzed chloro-arylsulfonylation of styrene derivatives; (16) Cu-catalyzed synthesis of 5-carboxyl-4-perfluoroalkyl triazoles; (17) Cross-nucleophile coupling of β-allenyl silanes with tertiary C–H bonds to access 1,3-dienes; (18) Cu-catalyzed C­( sp 3 )–H functionalization of O -pentafluorobenzoyl ketone oximes; (19) Total regioselectivity of hydrobromination of alkenes controlled by Fe or Cu catalyst; (20) Enantioselective synthesis of trifluoromethyl cyclopropylboronates by Cu catalysis; (21) Cu-catalyzed asymmetric cyclization of alkenyl diynes; (22) Synergistic Ir/Cu catalysis for asymmetric allylic alkylation of oxindoles; (23) Hydrosilylation of alkynes and alkenes with Cu-photocatalysis under continuous flow conditions; (24) Cu-based water oxidation catalysts with consecutive ligand-based electron transfer; (25) Heteroleptic copper-based complexes for energy-transfer processes: E → Z isomerization and tandem photocatalytic sequences; (26) Copper-catalyzed aminoheteroarylation of unactivated alkenes through distal heteroaryl migration; (27) Copper-catalyzed syntheses of multiple functionalized allenes via three-component reaction of enynes; (28) Unified mechanistic concept of the copper-catalyzed and amide-oxazoline-directed C­(sp 2 )–H bond functionalization; (29) Cu-catalyzed C–H allylation of benzimidazoles with allenes; (30) Synthesis of 1,2-aminoalcohols through enantioselective aminoallylation of ketones by Cu-catalyzed reductive coupling; (31) Copper-catalyzed N-directed distal C­(sp 3 )–H sulfonylation and thiolation with sulfinate salts; and (32) Dehydrogenative aza-[4 + 2] cycloaddition of amines with 1,3-dienes via dual catalysis …”

Asymmetric Synthesis of Tertiary and Secondary Cyclopropyl Boronates via Cyclopropanation of Enantioenriched Alkenyl Boronic Esters

“…While several methods are known in the literature for the preparation of secondary cyclopropyl boronates enantioselectively (Scheme a), − there are limited methods to prepare tertiary cyclopropyl boronates . In fact, only one protocol exists for their preparation, which is limited to accessing 1,2-diarylated cyclopropanes. , …”