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Ah ighly efficient kinetic resolution and dynamic kinetic resolution of chromene is reported for the first time and they procced by arhodium-catalyzed asymmetric hydroarylation pathway.T his new approach offers versatile access to various chiral 2,3-diaryl-chromanes containing vicinal stereogenic centers,a sw ell as the recovered chiral flavenes,i nh igh yields with excellent ee values (s factor up to 532). Particularly noteworthy is that this strategy can be further extended to the establishment of adynamic version of the kinetic resolution of chromene acetals and allows complete access to chiral isoflavanes and a-aryl hydrocoumarins.Flavonoids are privileged structural motifs in numerous natural products and pharmaceutical molecules which show many biological activities such as antitumor,a ntioxidant, antibacterial, and anti-inflammatory properties. [1] Flavene, flavane,a nd isoflavane,w hich feature ac hiral center, are subgroups of flavonoids ( Figure 1). Given the prevalence of this structural unit there has been considerable interest in developing methods for the generation of flavene skeletons. Nevertheless,f acile access of their corresponding optically active variants by asymmetric catalysis remains limited. [2] Rhodium-catalyzed asymmetric arylation has been intensively investigated in recent years,however,the alkenes were limited mainly to those activated by proximal electronwithdrawing substituents (represented by carbonyl groups). [3] In fact, examples concerning the rhodium-catalyzed asymmetric arylation of alkenes are rare.I n2 008, Lautens and co-workers reported an asymmetric hydroarylation process in the reaction of ab icyclo[2.2.1]heptane system. [4] Recently,H ayashi and co-workers also reported several successful examples of asymmetric hydroarylations of cycloalkenes. [5] To the alkenylarene substrates,L autens reported the rhodium-catalyzed asymmetric addition of arylboronic acid compounds to simple styrenes and it resulted in Heck-type products,owing to the alkylrhodium intermediate often prefering b-hydride elimination rather than protonation (Scheme 1a). [6] Thea symmetric hydroarylation of styrene was realized by Lam and co-workers where the strongly electron-withdrawing group (nitro) at the paraposition of the arene was aprerequisite to afford the desired hydroarylation product (Scheme 1b). [7] Thus,weselected 2Hchromene skeletons as substrates,i nw hich the arylrhodium intermediates do not have syn b-hydrogen atoms for bhydrogen elimination, and would thus undergo protonation to give hydroarylation products.We embarked on this investigation using the rac-flavene 1aas the benchmark substrate and phenylboronic acid (2a)as the arylating agent (Table 1). To our delight, the arylation product 3aa,w ith vicinal chiral centers,w as obtained as as ingle diastereomer in 48 %y ield with 94 % ee,a nd the recovered 1a was also obtained in 31 %y ield with 95 % ee, catalyzed by the chiral Rh complex in situ generated from 2.5 mol %[ Rh(cod)Cl] 2 and 6mol %( R)-Binap (entry 1). With the hopeful ini...

A transition-metal-free single electron transfer reaction has been developed for the synthesis of [D]-alkenes from terminal alkynes using sodium dispersions as the electron donor and EtOD- d as the deuterium source. Both reagents are cost-effective and bench-stable. This practical method exhibits remarkable terminal alkyne selectivity and exclusive alkene selectivity. Excellent deuterium incorporations and yields were achieved across a broad range of terminal alkynes without olefin isomerization. Of note, this reaction is highly solvent dependent. n-Hexane provides unique enhancement to this reductive deuteration process.

The first general reductive deuteration of nitriles under single-electron transfer conditions has been developed for the synthesis of α,α-dideuterio amines. This practical and cost-efficient protocol requires only bench stable and commercially available sodium dispersions and EtOD- d and allows for the reductive deuteration of a variety of nitriles in excellent yields and deuterium incorporations.

The first single electron transfer reductive deuteration of nitriles using D2O as a deuterium source has been developed for the synthesis of valuable α,α-dideuterio amines. A mild reductant (SmI2) was employed as the electron donor with Et3N as the additive. This reaction is amenable to both aromatic and aliphatic nitriles and features high deuterium incorporation, excellent regioselectivity, and good functional group tolerance. The synthetic utility of this protocol was demonstrated by the synthesis of a series of important deuterium-labeled building blocks for medicinal chemistry and agrochemistry applications.