ABSTRACT
Amines containing bridged bicyclic carbon skeletons are desirable building blocks for medicinal chemistry. Herein, we report the conversion of bicyclo[1.1.1]pentan-1-amines to a wide range of polysubstituted bicyclo[3.1.1]heptan-1-amines through a photochemical, formal (4 + 2)-cycloaddition of an intermediate imine diradical. To our knowledge, this is the first reported method to convert the bicyclo[1.1.1]pentane skeleton to the bicyclo[3.1.1]heptane skeleton. Hydrolysis of the imine products gives complex, sp3-rich primary amine building blocks.
Subject(s)
Alkenes/chemistry , Bridged Bicyclo Compounds/chemistry , Imines/chemistry , Cycloaddition Reaction , Hydrolysis , Pentanes/chemistry , StereoisomerismABSTRACT
A simple metal-free method has been developed for the reductive N-alkylation of indoles employing aldehydes as the alkylating agent and inexpensive Et3SiH as the reductant. A wide range of aromatic and aliphatic aldehydes are viable substrates along with a variety of substituted indoles. In addition, the method was applied to a one-pot sequential 1,3-alkylation of a substituted indole and successfully demonstrated on a 100 mmol scale.
ABSTRACT
Despite recent advancements in metal-catalyzed borylations of aryl (pseudo)halides, there is a continuing need to develop robust methods to access both early-stage and late-stage organoboron intermediates amendable for further functionalization. In particular, the development of general catalytic systems that operate under mild reaction conditions across a broad range of electrophilic partners remains elusive. Herein, we report the development and application of three catalytic systems (two Pd-based and one Ni-based) for the direct borylation of aryl (pseudo)halides using tetrahydroxydiboron (B2(OH)4). For the Pd-based catalyst systems, we have identified general reaction conditions that allow for the sequestration of halide ions through simple precipitation that results in catalyst loadings as low as 0.01 mol % (100 ppm) and reaction temperatures as low as room temperature. We also describe a complementary Ni-based catalyst system that employs simple unligated Ni(II) salts as an inexpensive alternative to the Pd-based systems for the borylation of aryl (pseudo)halides. Extrapolation of all three systems to a one-pot tandem borylation/Suzuki-Miyaura cross-coupling is also demonstrated on advanced intermediates and drug substances.
