C2-Symmetric tetrafluorobenzobarrelenes as highly efficient ligands for the iridium-catalyzed asymmetric annulation of 1,3-dienes with 2-formylphenylboron reagents

New C2-symmetric chiral diene ligands bearing a tetrafluorobenzobarrelene framework were prepared via a [4+2] cycloaddition of 1,4-bis((methoxymethoxy)methyl)benzene with tetrafluorobenzyne. The diene ligands realized the iridium-catalyzed enantioselective [3+2] annulation of 1,3-dienes with 2-formylphenylboron reagents giving 1-indanol derivatives in high yields and with high enantioselectivities.

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2,5-Bis[(methoxymethoxy)methyl]-7,8-tetrafluorobenzobicyclo[2.2.2]octatrieneC18H18F4O4Ee = 100%[α]D20=-8.2 (c 0.97, CHCl3)Source of chirality: resolution by chiral HPLC (Chiralcel OD-H)Absolute configuration: (1R,4R)

2,5-Bis(hydroxymethyl)-7,8-tetrafluorobenzobicyclo[2.2.2]octatrieneC14H10F4O2Ee = 100%[α]D20=-17.2 (c 1.02, CHCl3)Absolute configuration: (1R,4R)

2,5-Bis(bromomethyl)-7,8-tetrafluorobenzobicyclo[2.2.2]octatrieneC14H8Br2F4Ee = 100%[α]D20=-31.1 (c 0.99, CHCl3)Absolute configuration: (1R,4R)

2,5-Dibenzyl-7,8-tetrafluorobenzobicyclo[2.2.2]octatrieneC26H18F4Ee = 100%[α]D20=+28.4 (c 1.00, CHCl3)Absolute configuration: (1R,4R)

2,5-Bis[(triphenylsiloxy)methyl]-7,8-tetrafluorobenzobicyclo[2.2.2]octatrieneC50H38F4O2Si2Ee = 100%[α]D20=+11.1 (c 1.04, CHCl3)Absolute configuration: (1R,4R)

3-Methyl-3-vinyl-2,3-dihydro-1H-inden-1-olC12H14OEe = 95%[α]D20=+30.3 (c 1.06, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1S,3S)

3-Benzyl-3-vinyl-2,3-dihydro-1H-inden-1-olC18H18OEe = 94%[α]D20=+56.9 (c 0.84, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1S,3S)

(1S,2R,3R)-2-Hexyl-3-vinyl-2,3-dihydro-1H-inden-1-olC17H24OEe = 93%[α]D20=+80.0 (c 0.89, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1S,2R,3R)

2-[2-(tert-Butyldimethylsiloxy)ethyl]-3-vinyl-2,3-dihydro-1H-inden-1-olC19H30O2SiEe = 92%[α]D20=+39.9 (c 0.97, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1S,2R,3R)

Methyl 2-(1-hydroxy-3-vinyl-2,3-dihydro-1H-inden-2-yl)acetateC14H16O3Ee = 92%[α]D20=+94.4 (c 1.05, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1S,2R,3R)

3-Methyl-3-vinyl-2,3-dihydro-1H-inden-1-yl tosylcarbamateC20H21NO4SEe = >99%[α]D20=-17.2 (c 0.55, CHCl3)Source of chirality: asymmetric synthesisAbsolute configuration: (1S,3S)