April 2024

1,1-Diborylalkene, a class of important diboryl species, serves as the synthetic precursor of multisubstituted olefin, which is a prevalent building block in natural products, functional materials, and pharmaceuticals. Current methods mainly afford symmetrical 1,1-diborylalkenes, and late-stage differentiation of the two identical boryl groups is required to achieve selective difunctionalization. In comparison, stereoselective synthesis of unsymmetrical 1,1-diborylalkenes (UDBA) are less-explored. This Synpacts article provides a brief summary of the achievements in the synthesis of UDBAs. In particularly, we highlight our recent work on the unsymmetrical 1,1-diborylation of alkynes using a neutral sp2–sp3 diboron reagent to access UDBAs and their controllable stepwise derivatization.1 Introduction2 Background: Unsymmetrical 1,1-Diborylalkene Synthesis3 Stereoselective Unsymmetrical 1,1-Diborylation of Alkynes with a Neutral sp2–sp3 Diboron Reagent4 Summary and Outlook

Organic chromophores emerged as diverse functional materials in the areas of organic catalysis, toxic materials sensing, bio-imaging, and organic electronic devices. With rich chemical and electronic structures, main-group elements have been extensively implanted in organic chromophores to fine-tune the chemical/electronic structures and optoelectronic properties. In this Synpact article, we present a concise overview of the development of phosphorus (P)-containing organic chromophores, further highlighting our recent contributions in the field. A new aspect of combining the P element with the indole moiety was pursued to construct a new series of seven-membered P-organic chromophores; namely, indole-functionalized phosphepines. The new combination endowed the system with rich chemical and electronic structures, for which intriguing photophysical properties were consequently revealed. The combination provided an efficient synthetic protocol to access new P-heterocycles and also offered a new strategy to design functional organic chromophores.

Heteroatom-based olefinating reagents (e.g., organic phosphonates, sulfonates, etc.) are used to transform carbonyl compounds into alkenes, and their mechanism of action involves aldol-type addition, cyclization, and fragmentation of four-membered ring intermediates. We have developed an analogous process using ethyl 1,1,1,3,3,3-hexafluoroisopropyl methylmalonate, which converts electrophilic aryl aldehydes into α-methylcinnamates in up to 70% yield. The reaction plausibly proceeds through the formation of β-lactone that spontaneously decarboxylates under the reaction conditions. The results shed light on the Knoevenagel–Doebner olefination, for which decarboxylative anti-fragmentation of aldol-type adducts is usually considered.