Electrochemically Driven Desaturation of Carbonyl Compounds

Abstract

<jats:p>&lt;p&gt; Electrochemical techniques have long been heralded for their innate sustainability as efficient methods for achieving redox reactions. Carbonyl desaturation, as a fundamental organic oxidation, is an oft-employed transformation to unlock adjacent reactivity. To date, the most reliable methods for achieving it have relied on transition metals (Pd/Cu) or stoichiometric reagents based on I, Br, Se, or S. Herein we report an operationally simple pathway to such structures from enol silanes and phosphates using electrons as the primary reagent. This electrochemically driven desaturation exhibits a broad scope across an array of carbonyl derivatives, is easily scalable (1-100g), and can be predictably implemented into synthetic pathways using experimentally or computationally derived NMR shifts. Mechanistic interrogation suggests a radical-based reaction pathway. &lt;br&gt;&lt;/p&gt;</jats:p>

Insertion of ammonia into alkenes to build aromatic N-heterocycles

“…First, the reaction starts with anodic oxidation of alkene 1 and the subsequent trapping of cationic radical A with ammonia (for more details of the radical kinetics, see Supplementary Figs. [15][16][17][18][19].…”

“…Such an intrinsic obstacle makes the direct insertion of heteroatoms into alkenes to build heterocycles an elusive goal. To regulate the oxidation state of organic molecules, the dehydrogenation reaction is a complementary route to the oxygenation reaction [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] . Dehydrogenative cross-coupling exhibits a unique ability to achieve oxidative bond formation in the absence of external oxidants [22][23][24][25][26] .…”

Carbonyl Desaturation: Where Does Catalysis Stand?

“…43 Earlier this year, our group reported an electrochemically driven desaturation (EDD) method to address this challenge (Figure 5B). 44 Notably, this method exhibits a broad scope across an array of carbonyl derivatives such as ketones (86, 87, and 92), aldehydes (90), esters (88, 91), and lactams (89). In addition, this oxidation protocol can simply be performed in an undivided cell, without strict removal of air or water, and in the absence of expensive metals, ligands, or stoichiometric chemical oxidants.…”

Cobalt-electrocatalytic HAT for functionalization of unsaturated C–C bonds

“…28 The method of Norton, which relies on a high pressure of hydrogen gas, delivered only traces of product (entry 2). 29 First forays into e-HAT isomerization followed the guiding principles 29 from prior findings in electrochemistry 31,32 and HAT chemistry 33 to aid in the selection of proper ligands, cathodic materials and proton sources. An abbreviated summary of over 200 experiments is depicted in Figure 1D (see SI for an extensive list).…”

“…With this new set of conditions in hand, a range of substituted alkynes could be reduced with e-HAT to provide Z-alkenes in good yield (Table 2) rapidly. Boc-protected amines (32), pyridines (33), ethers (34), free and silyl-protected alcohols (36,41), aryl chlorides (37), aryl-BPin (38), carbonyls (39,42), alkenes (39), and phosphates (40) were all tolerated. The highest Z/E selectivity was observed with primary-, secondary-, and tertiary carbons adjacent to the alkyne moiety.…”