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Herein we report the cycloisomerization of electron-poor 1,5-dienes via the β-azolium ylide to give enantioenriched cyclopentenes. The reaction is mediated by a chiral N-heterocyclic carbene (NHC) catalyst, exploits readily available substrates, has good generality (17 examples), and displays excellent enantioselectivity (mostly >94:6). Studies demonstrating the viability of a related dynamic kinetic resolution are reported, as are those with alternate tethers and derivatizations.

Direct polarity inversion of conjugate acceptors provides av aluable entry to homoenolates.N -heterocyclic carbene (NHC) catalyzedr eactions,i nw hich b-unsubstituted conjugate acceptors undergo homoenolate formation and C À C bond formation twice,h ave been developed. Specifically,t he all-carbon (5+ +1) annulations give ar ange of mono-and bicyclic cyclohexanones (31 examples). In the first family of annulations, b-unsubstituted acrylates tethered to ad ivinyl ketone undergo cycloisomerization, providing hexahydroindenes and tetralins.I nt he second, partially untethered substrates undergo an intermolecular (5+ +1) annulation involving dimerization followed by cycloisomerization. While enantioselectivity was not possible with the former,t he latter proved viable,a llowing cyclohexanones to be produced with high levels of enantiopurity (most > 95:5 e.r.)a nd exclusive diastereoselectivity (> 20:1 d.r.). Derivatizations and mechanistic studies are also reported. Scheme 1. Backgrounda nd mechanistic framework. EWG = electronwithdrawinggroup.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Herein we report the cycloisomerization of electronpoor 1,5-dienes via the b-azolium ylide to give enantioenriched cyclopentenes.T he reaction is mediated by ac hiral N-heterocyclic carbene (NHC) catalyst, exploits readily available substrates,h as good generality (17 examples), and displays excellent enantioselectivity (mostly > 94:6). Studies demonstrating the viability of arelated dynamic kinetic resolution are reported, as are those with alternate tethers and derivatizations.

Direct polarity inversion of conjugate acceptors provides a valuable entry to homoenolates. N‐heterocyclic carbene (NHC) catalyzed reactions, in which β‐unsubstituted conjugate acceptors undergo homoenolate formation and C−C bond formation twice, have been developed. Specifically, the all‐carbon (5+1) annulations give a range of mono‐ and bicyclic cyclohexanones (31 examples). In the first family of annulations, β‐unsubstituted acrylates tethered to a divinyl ketone undergo cycloisomerization, providing hexahydroindenes and tetralins. In the second, partially untethered substrates undergo an intermolecular (5+1) annulation involving dimerization followed by cycloisomerization. While enantioselectivity was not possible with the former, the latter proved viable, allowing cyclohexanones to be produced with high levels of enantiopurity (most >95:5 e.r.) and exclusive diastereoselectivity (>20:1 d.r.). Derivatizations and mechanistic studies are also reported.