Non-isocyanate polyurethanes (NIPUs) constitute a promising alternative for more classical polyurethanes (PUs) as they may display mechanical properties that can match those of PUs and their synthesis does not involve the use of toxic isocyanates.
The stereospecific cross-coupling of enantioenriched non-benzylic secondary alkyl boron compounds has been achieved. The high selectivity toward product formation over an undesired β-H elimination pathway is achieved via an intramolecular coordination of an ancillary carbonyl to the metal center in the diorganopalladium intermediate.
Enantiomerically enriched potassium β-trifluoroboratoamides were synthesized as air stable solids in greater than 95:5 dr using pseudoephedrine as the chiral auxiliary. With these chiral nucleophiles, Suzuki-Miyaura cross-coupling reactions were carried out with various aryl- and hetaryl chlorides in good to excellent yields. Moreover the diastereoselectivities were preserved throughout the Suzuki–Miyaura cross-coupling reactions.
The aminolysis of (poly)carbonates by (poly)amines provides access to non-isocyanate polyurethanes (NIPUs) that are toxic-reagent-free analogues of polyurethanes (PUs). Owing to their low reactivity, the ring opening of cyclic carbonates requires the use of a catalyst. Herein, we report that the more available and cheaper ureas could advantageously be used for catalyzing the formation of NIPUs at the expense of the thiourea analogues. In addition, we demonstrate a medium-range pKa of the (thio)urea and an unqeual substitution pattern is critical for controlling the efficiency of the carbonate opening.
Organotrifluoroborates are partners for cross‐coupling that have emerged as complementary and often unique alternatives to other organoboron reagents. This chapter provides a comprehensive overview of all cross‐coupling reactions of the various classes of organotrifluoroborates that have been carried out through August, 2009.
The chapter introduces the subject with a discussion of mechanistic considerations concerning the cross‐coupling, followed by a brief discussion of the stereochemical aspects of the transformation. The scope and limitations of the reactions are subsequently discussed, first in terms of the organotrifluoroborate and then the electrophilic partner of the reaction.
Potential side reactions that are encountered are outlined with useful suggestions on how these can be avoided in practice. Applications in synthesis are described, detailing how organotrifluoroborates have been utilized in the construction of natural products, materials of all types, and pharmacologically active substances. A comparison to other cross‐coupling methods rounds out the descriptive part of the chapter.
A detailed outline of experimental considerations and protocols has been assembled, gleaning information from the vast array of published procedures to assemble an overview of the most successful conditions. Representative procedures are included for each class of organotrifluoroborate coupling partner, and the tables provide a comprehensive listing of individual reactions.
This feature article summarizes the different strategies for the synthesis of [a]-benzo-fused BODIPYs that have been reported in the literature until 2018.
Potassium beta-aminoethyltrifluoroborates were prepared in good yields via hydroboration of the corresponding enecarbamates using the Snieckus hydroborating reagent. A wide variety of phenethylamines containing a potentially free primary amine after appropriate deprotection have been successfully prepared in good yield using these organotrifluoroborates as partners in Suzuki-Miyaura coupling with aryl bromides, iodides, and triflates.
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