Metal‐Free Allene‐Based Synthesis of Enantiopure Fused Polycyclic Sultones

Abstract

The controlled metal-free preparation of fused δ-sultone derivatives has been developed starting from hydroxyallenynes. The use of 2-(3,3-diethyltriaz-1-enyl)-4-methylbenzene-1-sulfonyl chloride in a sulfonylation/rearrangement sequence gives access to 1,3-dien-2-yl arenesulfonates. These functionalized enynes suffered a direct cyclization/desaturation radical cascade, allowing the synthesis of a variety of enynyl [1,2]oxathiine 1,1-dioxides. Stereoselective cyclization of the readily formed core through intramolecular Diels-Alder reaction has also been demonstrated, affording β-lactam- and glucofuranoside-fused δ-sultone polycycles. These selective reactions have been studied experimentally and additionally, their reaction mechanisms have been investigated computationally by means of density functional theory calculations.

Deciphering the Chameleonic Chemistry of Allenols: Breaking the Taboo of a Onetime Esoteric Functionality

“… 186 On the other hand, related [3,3]-sigmatropic transposition of arylsulfonyl allenes produced dienes 159b or 159c , which are employed to the synthesis of enantiopure polycyclic sultones such as 162b or 162c trough a two-step sequence ( Scheme 30 , reactions b and c). 187 …”

“…The formal OH migration to yield dienes 159 is proposed to proceed through a six membered ring transition state 158 (Scheme ). , DFT calculations supported an aromatic transition state in accordance to a pericyclic reaction mechanism, in view of a negative nucleus independent chemical shift obtained at the ring critical point of the electron density (NICS = −6.5 ppm). Also, a low calculated activation barrier of only 17.7 kcal/mol shows coincidence with the mild experimental reaction conditions needed for the transformation.…”

“…In one hand, a tandem [3,3]-sigmatropic rearrangement/Diels–Alder reaction provided optically pure tricyclic β-lactams such as 160 (Scheme , reaction a) . On the other hand, related [3,3]-sigmatropic transposition of arylsulfonyl allenes produced dienes 159b or 159c , which are employed to the synthesis of enantiopure polycyclic sultones such as 162b or 162c trough a two-step sequence (Scheme , reactions b and c) …”

Progress in the synthesis of δ-sultones

“…Carefully chosen control experiments clearly support a radical mechanism for this transformation [ 82 ]. Very recently, Alcaide, Almendros, and co-workers developed a metal free radical cyclization strategy to access highly functionalized δ-sultones 64 starting from the radical precursor 62 and TEMPO ( 63 ) in the presence of trifluoroacetic acid [ 83 ]. Noteworthy, a variety of highly functionalized starting materials 62 (with rather complex R-groups) were obtained in a very elegant fashion from allene precursors and the interested reader is kindly referred to the original paper for more details concerning this interesting procedure [ 83 ].…”

Updating the CSIC Reaction (2003–2020)

“…Consequently, and advancing our apologies for involuntary oversights and uncited articles, we decided to update and summarize the developments of CSICr from 2003, including SciFinder ® search as noted above, the contributions for the most dedicated CSICr practitioners, highlighting author contributions who cited the CSICr name reaction in the context of their research, [12] or communications citing [13] the seminal review [1] . In particular, two contributions deserve special comments, as new and efficient non CSICr‐methods for the synthesis of fused δ‐sultone derivatives starting from hydroxyallenynes, [13c] or for the preparation of benzosultams via visible light‐promoted and gold‐photoredox‐catalyzed reactions of sulfonamide tethered alkynes with arenediazonium salts [13d] …”