We developed an effective method for reductive radical formation that utilizes the radical anion of carbon dioxide (CO 2•− ) as a powerful single electron reductant. Through a polarity matched hydrogen atom transfer (HAT) between an electrophilic radical and a formate salt, CO 2•− formation occurs as a key element in a new radical chain reaction. Here, radical chain initiation can be performed through photochemical or thermal means, and we illustrate the ability of this approach to accomplish reductive activation of a range of substrate classes. Specifically, we employed this strategy in the intermolecular hydroarylation of unactivated alkenes with (hetero)aryl chlorides/bromides, radical deamination of arylammonium salts, aliphatic ketyl radical formation, and sulfonamide cleavage. We show that the reactivity of CO 2•− with electron-poor olefins results in either single electron reduction or alkene hydrocarboxylation, where substrate reduction potentials can be utilized to predict reaction outcome.
The dearomative cyclization of linear
amides to complex spirocyclic
butyrolactams has been enabled by photoredox catalysis through a reductive
radical–polar crossover mechanism. This mechanism operates
with precision on unactivated aromatic substrates to give a wide range
of 1,4-hydroalkylation products. This method utilizes a simple organic
catalyst/reductant pair to deliver products in a highly flexible manner
with respect to substitution, and the products can be further functionalized
under simple conditions to afford a collection of motifs. The mechanistic
analysis performed here outlines the salient features of this strategy,
which were applied to prepare a collection of complex scaffolds including
the anticonvulsive agent gabapentin.
This study began with the goal of
identifying additional constituents
from Zyzzya fuliginosa extracts obtained from an
Indo-Pacific sponge (coll. no. 06132). The previous work identified
several red and green pyrroloiminiquinones (aka pyrrolo[4,3,2-de]quinolines), and this reinvestigation provided two additional
analogues, a blue compound named zyzzamine A (1) and
a green compound named zyzzamine B (2). The relatively
low ratio of H/[sum(CNO)] = 0.71 or 0.76 of this pair greatly complicated
the final steps of compound characterization and required the use
of five 2D NMR strategies and MS2 data sets.
A new visible-light-driven method for the carboxylation of (hetero)aryl/vinyl bromides has been developed using catalytic 4CzIPN, nickel, phenyl triflimide, and sodium formate as a carboxylation agent. Interestingly, we found catalytic phenyl triflimide plays an essential role in promoting the reaction. While many C(sp 2 ) carboxylation reactions require harsh reagents or gaseous carbon dioxide, we demonstrate the mild and facile construction of carboxylic acids from readily available starting materials.
Indonesian marine sponges, especially Jaspis cf. coriacea and Jaspis splendens are sources for families of natural products known as the bengamides and jasplakinolides, respectively. Recent research suggests that the biosynthetic origins of these pharmaceutically important compounds may not be the sponges themselves but associated Gram-negative bacteria. Therefore samples of J. cf. coriacea and J. splendens were collected to culture the bacteria responsible for such compounds. Metabolomic analysis was performed on each of the sponges collected to ensure that the bengamides and jasplakinolides were present; therefore ensuring that the biosynthetic machinery required to produce these compounds was intact in the samples. After which Gramnegative bacteria were cultured from the Jaspis sponge samples and a total of 43 unique isolates were obtained spanning 21 taxonomic genera and three taxonomic classes.
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