Divergent ynamide reactivity in the presence of azides – an experimental and computational study

Abstract

An unusually divergent reactivity of ynamides in the presence of azides is reported.

Unusual mechanisms in Claisen rearrangements: an ionic fragmentation leading to a meta-selective rearrangement

“…Based on the putative mechanism outlined in Scheme 2 , we were eager to verify whether certain key charged intermediates [ 3 + Y] + (Y = H, Na), 4 + , 5 + and 6 + ( Scheme 2 ) could be intercepted and characterised via electrospray ionisation MS operated in positive-ion mode (ESI(+)-MS). 12 …”

Keteniminium Ions: Unique and Versatile Reactive Intermediates for Chemical Synthesis

“…Such nucleophiles include alkyl azides, which were previously shown to react with non-activated keteniminium ions (Scheme 7), 27 whose reaction with yneoxazolidinone-derived keteniminium triflates 149 yield transient aminovinyltriazinium triflates 150 that undergo, after extrusion of nitrogen, a series of ring-closure and ringopening reactions yielding, after hydrolysis, oxazolidine-2,4-diones 152 (Scheme 31). 97 Starting from sulfonyl-protected ynamines and benzylic azides, a concerted deprotonation/protonation yielding 2-azabuta-1,2-dienes occurs after the extrusion of nitrogen. 98 Switching to dioxazoles, 153 promotes another rearrangement from aminovinyldioxazolium ions 154 affording 4-aminooxazoles 155 resulting from a formal [3+2] cycloaddition.…”

Synthesis of γ-substituted carbonyl compounds from DMSO-mediated oxidation of enynamides: mechanistic insights and carbon- and hetero-functionalizations

“…To gain a mechanistic insight into the remote Umpolung functionalizations and to probe the nature of the intermediates involved, kinetic analysis was conducted. To the best of our knowledge, kinetic analysis on the Brønsted acid-catalyzed oxidative coupling of ynamides that can be used to check the validity of the DFT theoretical studies13e,22 is unavailable. We set out to perform a Hammett study with a set of enynamides differing in para -substituents, 4b (4-OMe), 4c (4-Me), 4d (4-H), 4e (4-Cl), 4p (4-Ph), and 4q (4-Br) to probe the electronic effect of aryl groups at C4 according to eqn (1) (Scheme 2).…”