NEWS OF THE WEEK
DOUBLE TIME FOR CROSS-COUPLING ORGANIC CHEMISTRY: Merging two fundamental organoboron reactions provides a new synthetic platform N A CASE OF TEACHING an old dog a new trick,
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(1,2-metallate rearrangement), resulting in formation of two new bonds that meld the boron center, ligand, and electrophile together into the product molecule. Chemists have generally explored these two reactions as separate occurrences. But the Morken group found a way to splice them together in a one-pot reaction. The team uses an organolithium reagent with an organoboron reagent to generate a boronate species that is intercepted by an electrophilic palladium species containing a chiral ligand that is formed by oxidative addition. The intermediate doesn’t undergo the typical SuzukiMiyaura transmetallation step with the vinyl boronate but instead adds to the π bond of the Pd vinyl boronate, triggering a Ar X 1,2-metallate rearrangement.
Boston College researchers have discovered how to merge two important chemical transformations involving widely used organoboron reagents into one. Liang Zhang, James P. Morken, and Oxidative 1,2-Metallate Li coworkers combined key steps of the B(OR)2 rearrangement, addition intermediate Organolithium reductive elimination Chiral Pd catalyst Ar X Suzuki-Miyaura cross-coupling cataAr Aryl halide + R1 lytic cycle with a stoichiometric metalLi or triflate R1 B(OR)2 late rearrangement process to generate – 1 B(OR)2 Organoboron R a multicomponent catalytic reaction TWO TO ONE Boronate that delivers chiral products. This new Conjunctive cross(OR)2 = neopentylglycol, R1 = alkyl or aryl intermediate concept, which they call conjunctive coupling combines cross-coupling, could have major implications in the Following a reductive elimination step, the overall transmetallation broad field of cross-coupling reactions (Science 2016, reaction leads to formation of two new C–C bonds and a steps from two DOI: 10.1126/science.aad6080). new C–B stereocenter, delivering the product molecule reactions to create Suzuki-Miyaura cross-coupling typically proceeds by with high enantioselectivity. The products are convea new reaction insertion of a palladium catalyst into the carbon-halogen nient organoboron compounds that can be oxidized to pathway to chiral bond of an aryl halide electrophile (oxidative addition). alcohols or used as reagents in sequential syntheses. products. This process is followed by a ligand passing from an or“It is astonishing that in the nearly 40-year history ganoboron reagent to palladium (transmetallation) and of what is probably the most-used organometalconcluded by the catalyst coupling the aryl group and lic reaction in organic synthesis—Suzuki-Miyaura ligand together via formation of a new C–C bond and coupling—a new pathway has been discovered,” says shedding the product molecule (reductive elimination). Varinder K. Aggarwal, an organoboron specialist at In contrast, noncatalytic stoichiometric processes the University of Bristol. “Perhaps this achievement with organoboron reagents operate by addition of a reflects our still-limited understanding of some of the metal partner such as an organolithium reagent to the key steps in cross-couplings. But those brave enough organoboron reagent to form an intermediate metal bor- to challenge the dogma of what really goes on during onate complex. Addition of an electrophilic reagent then the transmetallation step may find further rich veins promotes migration of the organoboron reagent’s ligand of untapped opportunities.”—STEVE RITTER
RESTRUCTURING Amid layoffs, DuPont R&D chief defends corporate research role Doug Muzyka, DuPont’s chief science and technology officer, says the company’s reorganization of R&D in advance of its merger with Dow Chemical does not mean an end to corporate research at DuPont. But as pink slips drop on desks at the company, it is becoming clear that Central R&D is being severely truncated. C&EN recently reported that DuPont will replace Central Research & Development with a new organization dubbed Science & Innovation. Concurrently, DuPont will eliminate 1,700 positions in its home state of Delaware, including researchers, as part of a $700 million cost-
reduction program that will cut the company’s overall workforce by 10%. Muzyka claims recent media reports have “mischaracterized” the changes at DuPont by maintaining that “corporately funded R&D is being completely eliminated or that the cost-reduction effort at DuPont is targeting R&D.” However, according to a tally obtained by C&EN and unconfirmed by DuPont, of the 270 people working in Central R&D, 173 were laid off last week, 63 transferred to other DuPont businesses, and 34 were left in Science & Innovation. As part of the R&D restructuring,
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Muzyka says, “we are redesigning the existing Central Research & Development operating model to assess and seed new, transformational sciencebased ventures as the next step in the evolution of corporately funded R&D for DuPont.” The changes, he adds, will position the company for its merger with Dow and the subsequent breakup of the new DowDuPont into three firms. Muzyka says the cuts are the result of “careful analysis of how we can improve the overall productivity of our R&D function company-wide.”—ALEX TULLO
