Synthetic transformations using arenesulfonyloxy groups, first as electrophiles, then as leaving groups

Syntheses and transformations of α-azido ketones and related derivatives

“…Undoubtedly, the most frequent method for the synthesis of a-azido ketones 2 is the nucleophilic substitution of the corresponding a-substituted ketone 1 having a good leaving group such as a halide or, much more rarely, a sulfonyloxy unit (Scheme 1). The increased reactivity of a-halo 10,11 or sulfonyloxyketones 12 and the high nucleophilic power of the azide ion make this reaction easy. The first application of this reaction for the synthesis of an a-azido ketone was reported in 1908.…”

Bromo–nitro substitution on a tertiary α carbon—a previously uncharacterized facet of the Kornblum substitution

“…It has also been suggested that substitution is by S N 1 reaction, and that this is accelerated by neighbouring group participation by the carbonyl, creating a 2H-oxirenium cation [78], or by prior enolisation on the other side, creating an allylic system [79]; other suggestions include via a carbene produced from an enolate [67], and through nucleophilic attack at the halogen [32,41,67]. Evidence for each mechanism, and against other mechanisms, has been found by different workers in different reactions, and many writers give evidence that different mechanisms dominate in different circumstances [23,32,55,73]. In most papers Kornblum generally described the substitution as S N 2, but in one paper he described it as more S N 2 than S N 1 in nature, but with properties of both [80].…”

“…Some authors argue that addition takes place initially at the carbonyl, followed by either a 1,2-shi of the nucleophile to the alpha position, [41][42][43][44][45][46][47] or, alternatively, formation of an epoxide that reacts with further nucleophile at the alpha position. 40,[48][49][50][51][52][53][54][55] Other authors reject this and contend that the reacting nucleophile makes an ordinary S N 2-like attack at the carbon bearing the leaving group, but is assisted by interaction with carbonyl p* antibonding orbitals that temporarily accept electron density (oen described as conjugation with the p orbitals or the p system, or as an enolate-like transition state), 34,37,38,[56][57][58][59][60][61][62][63][64][65] or alternatively by purely electrostatic effects. 23,[66][67][68][69] More recently a halfway position between these two extremes has been urged: that the attacking nucleophile bridges the carbonyl and the alpha carbon (and, by the principle of microscopic reversibility, the leaving group must also bridge both positions).…”

The CP Molecule Labyrinth: A Paradigm of How Endeavors in Total Synthesis Lead to Discoveries and Inventions in Organic Synthesis

“…This advantage of α ‐sulfonated ketones, coupled with their stability and sometimes unique chemistry,58 prompted us to investigate them further. Thus, by tapping into the rich chemistry of related sulfonyloxy ketones,59 and by introducing our own modificaitons, we envisaged the naissance of a seamless and novel linker which would provide access to a wide ranging library of structural types 60…”