Copper-Catalyzed Difunctionalization of Allenes with Sulfonyl Iodides Leading to (E)-α-Iodomethyl Vinylsulfones

Abstract

A highly regioselective iodosulfonylation of allenes in the presence of CuI and 1,10-phenanthroline has been developed for the synthesis of various useful ( E)-α-iodomethyl vinylsulfones in moderate to excellent yields. This practical reaction is fast, operationally simple, and in particular, proceeds under very mild conditions to afford the target products with high regio- and stereoselectivity. The selectivity was illustrated by a conceptual DFT analysis.

A complementary approach to conjugated N-acyliminium formation through photoredox-catalyzed intermolecular radical addition to allenamides and allencarbamates

“…We envisaged that a route to the conjugated N-acyliminium intermediate could be achieved via an intermolecular addition of an electrophilic radical to an allenamide (1) followed by an oxidation process on the subsequently formed radical (Scheme 3) [41]. The thought process behind this approach is based on three observations; (i) Akita and co-workers disclosure on the photoredox-catalyzed oxytrifluoromethylation of allenes 6 to give 2-trifluoromethylated allyl acetates 7 [42][43][44]; (ii) that intramolecular radical cyclization of allenamides have been reported by Hsung and co-workers, where the radical adds principally to the central carbon of the allene (10) [45]; and (iii) the photoredox-catalyzed addition of radicals to enamides reported by Masson [46][47][48][49], and more recently by our own laboratory in the synthesis of [50]. Therefore, photoredox-catalysis would be employed to generate an electrophilic radical that would add to the central carbon of the allenamide 1 to give a transient radical 13, whose oxidation, facilitated by the photoredox catalyst [47,48], would provide the conjugated N-acyliminium 14.…”

Mechanistic Aspects and Synthetic Applications of Radical Additions to Allenes

“…In 2018, Lu et al published a regio- and stereoselective synthesis of ( E )-α-halomethyl vinylsulfones 181 and 183 via a Cu­(I)-catalyzed difunctionalization of allenes 180 and 182 . A 1.5:1 mixture of allene and sulfonyl iodide was subjected to a catalytic amount of CuI and 1,10-phenanthroline in dichloromethane at room temperature to produce various 1:1 adducts in moderate to excellent yield (Scheme ).…”

Metal- and Solvent-Free Ultrasonic Multicomponent Synthesis of (Z)-β-Iodo Vinylthiocyanates

“…However, to the best of our knowledge, there is no example of synthesis of β-iodo vinylthiocyanates through multicomponent reaction from cheap and readily available starting materials. With our continuing interest in green chemistry, − we have developed the environmentally friendly functionalization of alkynes. − In this paper, we herein report the ultrasound-assisted (sixth principle of green chemistry: design for energy efficiency) multicomponent synthesis (eighth principle of green chemistry: reduce derivatives) of ( Z )-β-iodo vinylthiocyanates from readily available alkynes, molecular iodine, , and KSCN under metal- and solvent-free conditions (first principle of green chemistry: prevention) (Scheme d).…”