Enantiomerically enriched tosyl-protected diarylmethylamines were rapidly prepared by the asymmetric addition of arylboronic acids to N-tosylaldimines under mild conditions in the presence of a catalyst prepared in situ from Rh(I) and a chiral diene ligand. This methodology offers access to diarylmethylamines in good yields with excellent chiral purity at room temperature using MeOH as a solvent and NEt3 as a base. Its synthetic utility was demonstrated by the preparation of (S)-1-phenyl-1,2,3,4-tetrahydroisoquinoline (14), an antagonist of the N-methyl-d-aspartate (NMDA) receptor.
A chiral rhodium(I)−diene catalyst enabled the one-step synthesis of β-aryl β-imido sulfones under mild reaction conditions. By selection of the chiral diene ligand L1a or L2, each enantiomer of the chiral β-aryl β-imido sulfone target can be accessed with high stereoselectivity. Demonstration of the scope of the reaction, which includes the synthesis of an N-protected chiral β-amino β-phenyl sulfone, culminated with the efficient synthesis of the heteroatom-rich active pharmaceutical ingredient apremilast.E nantioenriched β-amino sulfone derivatives are versatile synthons in synthetic chemistry 1,2 and display a wide range of biological activities as compounds of medicinal importance. 3 For example, the oral drug apremilast (Otezla) (Figure 1), which is an inhibitor of phosphodiesterase 4
The highly enantioselective conjugate addition of a variety of arylboronic acids to β-nitroacrylates is reported to provide optically active α-aryl β-nitropropionates in up to 70% yields and >99.5% ee's, which are useful building blocks for preparing chiral β-amino acids. The applicability of this transformation is demonstrated by converting 3aa into the β-amino acid 5 and transforming 3ap to β-amino ester 7 via reduction and reductive N-alkylation. The latter compound is a precursor for preparing ent-ipatasertib.
Herein we describe the design and synthesis of a novel family of bifunctional, chiral bicyclo[2.2.1]heptadiene ligands bearing aryl and secondary amido groups, and demonstrate their usefulness in the Rh -catalyzed enantioselective addition reaction of arylboronic acids to N-diphenylphosphinyl (N-DPP)-protected aldimines. Unlike the analogous Rh -catalysts comprising diene ligands substituted with aryl and carboxylic ester groups, or only with aryl groups, the addition reaction proceeded with high stereoselectivity. The protocol tolerated a range of N-DPP-aldimines and arylboronic acids, producing the desired optically active N-DPP-protected amines with yields between 31-99 % and with ee values up to 91-99 %. The synthetic utility of the method was demonstrated by the conversion of N-DPP-protected amine 3 ae into the antifungal agent, bifonazole (13).
An efficient and trans-diastereoselective Rh(I)-catalyzed 1,4-conjugate addition reaction of alkenylboronic acids and a homochiral (R)-4-silyloxycyclopentenone useful for the synthesis of derivatives of prostaglandins E and F is described for the first time. The reaction functions under mild conditions and is particularly rapid (≤6 h) under low power (50 W) microwave irradiation at 30 °C in MeOH in the presence of a catalytic amount of KOH. Under these conditions, 3 mol % of [RhCl(COD)] is typically required to produce high yields. The method also functions without microwave irradiation at 3 °C in the presence of a stoichiometric amount of KOH. Under these conditions, only 1.5 mol % of [RhCl(COD)] is needed, but the reaction is considerably slower. The method accepts a range of aryl- and alkyl-substituted alkenylboronic acids, and its utility has been demonstrated by the synthesis of PGF (dinoprost) and tafluprost.
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