Ah ighly regioselective and stereoselective 1,5addition of alkyl groupst oe nantioenriched donor-acceptor cyclopropanes 1 and bicyclic cyclopropanes such as 6aryl-1-methoxycarbonyl-3-oxabicyclo[3.1.0]hexan-2-ones 4 using aG rignard reagentw ith ac atalytic amounto f Cu(OTf) 2 (0.1 equivalent) afforded optically active diesters 2 or trans-a,b-disubstituted g-butyrolactones 5 with an excellent level of stereoinduction. An excesso ft he Grignard reagent is necessary to perform the 1,5-alkylation with high yields.I nt he reactiono ft he enantioenrichedb icyclic lactone 4,ahighly stereoselective 1,5-addition and subsequent highly trans-selective protonation of the magnesium enolate via keto-enol isomerization furnished the trans-a,b-disubstituted-g-lactones with three contiguous chiral centers with excellent enantioselectivity. Based on the results, we also proposed the mechanism through cluster ion pairs or as imple ion pairt or ationalize the high stereoselectivity of the reaction.Supportinginformation for this article can be found under http:// dx.

Transformations of enantioenriched donor‐acceptor (D−A) cyclopropylcarbinols to enantioenriched 1‐arylnaphthalenes that bear an ortho‐substituent on a benzene ring provided a successful chirality‐exchange method with a high level of stereoinduction. A central chirality‐transfer step, i. e., a Lewis‐acid‐mediated ring‐opening cyclization of enantioenriched D‐A cyclopropylcarbinols (97 to >99 % ee), afforded 1‐aryl‐1,2‐dihydronaphthalenes with an ortho‐substituent (Me, Br, OMe, OBn, or OiPr) on the benzene ring with high enantioselectivity (97 to >99 % ee). The central‐to‐axial chirality‐exchange step, i. e., the dehydrogenation of the obtained enantioenriched 1‐aryl‐1,2‐dihydronaphthalenes using DDQ, furnished the axially chiral 1‐arylnaphthalenes with high enantioselectivity (90 to >99 % ee). Importantly, we developed a highly enantioselective synthesis of a 1‐arylnaphthalene with an ortho‐alkoxy group on the benzene ring. Moreover, we improved the chirality exchange to furnish a 1‐arylnaphthalene with an ortho‐alkoxy‐substituted benzene ring in high yield with high ee.

An asymmetric total synthesis of tupichilignan A was achieved using enantioenriched donor–acceptor (D–A) cyclopropanes. The key steps include an asymmetric cyclopropanation using the Hayashi–Jørgensen catalyst, an oxy‐homo‐Michael reaction of a bicyclic D–A cyclopropane, an α‐benzylation of a γ‐lactone, a decarboxylation furnishing a trans‐α,β‐dibenzyl‐γ‐lactone, a configurational inversion of a hydroxy chiral center via oxidation, and a final reduction, all of which occur with high stereoselectivity. The spectral data of the diastereomer previously identified in the literature as tupichilignan A were found to be inconsistent with the reported data for the natural product. On the basis of the spectral data of both of the synthesized diastereomers, the structure of tupichilignan A was revised, and the absolute configuration of the 7 position of tupichilignan A was changed from R to S.

The first enantioselective total synthesis of a bioactive lignanamide was achieved with high enantiomeric excess. Key synthetic steps include an organocatalytic enantioselective cyclopropanation and a Lewis-acid-mediated chirality-transferring 5-endo-tet-type cyclization that proceeds with a very high degree of stereoinduction. The proposed mechanism of the key reaction is supported by the experimental results. Based on these experimental results, the 5-endo-tet-type cyclization of a cyclopropylcarbinol proceeds predominantly via an S N 1 mechanism with high trans-selectivity, which arises from the steric hindrance of the neighboring substituent. Minor pathways include the anchimeric participation of (i) the oxygen atom of the benzoyl group in an S N 2 mechanism and/or (ii) a benzenecoordinated transition state in an S N 1-like mechanism.