A silylation-based kinetic resolution has been developed for α-hydroxy lactones and lactams employing the chiral isothiourea catalyst (-)-benzotetramisole and triphenylsilyl chloride as the silyl source. The system is more selective for lactones than lactams, and selectivity factors up to 100 can be achieved utilizing commercially available reagents.

We report the first chemoselective, high yield synthesis of monosubstituted rhodocenium through a "η 5 → η 4 → η 5 " strategy detailing sequential nucleophilic addition and endohydride abstraction. Monosubstituted rhodocenium derivatives are then used as versatile synthons for the preparation of the first-ever vinyl monomers that allow controlled polymerizations including ROMP and RAFT, leading to rhodocenium-containing metallopolymers. Exploratory ion-exchange and self-assembly of this new class of polyelectrolytes cultivates the potential of side-chain rhodocenium-containing polymers. ■ INTRODUCTIONMetallopolymers combine inorganic metal centers with catalytic, magnetic, and electronic properties and organic polymeric frameworks with desirable mechanical and processing properties. 1−4 Among them, metallocenes are the most important foci, as the field has been particularly inspired by the seminal work on the preparation of ferrocene-based polymers by the Manners group in the early 1990s. 5,6 There are two major states of a metallocene: neutral metallocene and cationic metallocenium. Neutral metallocenes, predominantly 18-e ferrocene and ruthenocene, are widely explored. 7−15 In comparison, cationic metalloceniums are disproportionally biased, 16−22 mostly due to either their chemical instability (for 17-e metalloceniums) or synthetic challenges (for 18-e metalloceniums). As a matter of fact, cationic metalloceniums are fundamentally different from neutral metallocenes, as they are ionic, and can be hydrophilic or hydrophobic depending on their counterions. 1 Thus, integration of metalloceniums into polymeric frameworks would constitute a class of polyelectrolytes that are ubiquitous for a variety of applications ranging from traditional electrolyte chemistry to biomedical applications to membranes, to name just a few. 21,23−25 After the struggle in early years, cationic 18-e metalloceniumcontaining polymers have gained momentum over the past few years. 18−20,22 Recent efforts have overcome many key hurdles to make 18-e cobaltocenium-containing materials not just a curiosity. Synthetic methodologies on cobaltocenium-containing main-chain 19,20 and side-chain 26,27 polymers as well as dendrimers 28,29 have been established. Many of these materials have exhibited unprecedented properties such as peptide nuclear delivery, DNA complexation, and antimicrobial bioconjugates. 21,23,25 Compared with cobaltocenium, the isoelectronic 18-e rhodocenium is a nearly unexplored cationic metallocenium. 30−35 To the best of our knowledge, there are almost no reports on either Rh-or rhodocenium-containing polymers, 36,37 except that the Astruc group recently prepared rhodocenium-containing polymers and dendrimers via ionic interactions between parent substrates and unsubstituted rhodocenium. 31 However, the major dilemma is the lack of a synthetic platform for the preparation of rhodocenium derivatives (both mono-and disubstituted), monomers, and polymers. 30,33 Thus, potential electrolyte chemistry and utilities of rhodocenium ...

We describe an unusual net 2+2 cycloaddition reaction between boron alkylidenes and unactivated alkenes. This reaction provides a new method for construction of carbocyclic ring systems bearing versatile organoboronic esters. In addition to surveying the scope of this reaction, we provide details about the mechanistic underpinnings of this process, and examine application to the synthesis of the natural product aphanamal.

We describe an unusual net [2+2] cycloaddition reaction between boron alkylidenes and unactivated alkenes. This reaction provides a new method for the construction of carbocyclic ring systems bearing versatile organoboronic esters. Aside from surveying the scope of this reaction, we provide details about the mechanistic underpinnings of this process, and examine its application to the synthesis of the natural product aphanamal.

Triphenylsilyl chloride in combination with catalytic amounts of (‐)‐benzotetramisole (BAM) allows the non enzymatic kinetic resolution of α‐hydroxy esters and amides.