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Herein, we present a photoinduced deconstructive alkoxyamination of alkyl alcohols catalyzed by iron salts. This transformation involves the initiation of alkoxy radicals through chlorine radical‐induced alkoxy radical formation, followed by β‐scission and trapping of the resulting carbon radicals with 2,2,6,6‐tetramethylpiperidin‐1‐yl (TEMPO). This reaction exhibits a broad substrate scope (40 examples), including primary and secondary alcohols that are prone to oxidation by the combination of TEMPO and iron. Mechanistic investigations have revealed that enhanced coordination of the chloride ion with the iron center inhibits the OH oxidation process, thereby enabling the tolerance of primary and secondary alcohols. [ABSTRACT FROM AUTHOR]

A light‐driven radical oxy‐functionalization of non‐acidic aliphatic and benzylic C(sp3)−H bonds was achieved with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) in a single‐step by employing an aryl ketone as a sole catalyst. The transformation was initiated by homolysis of a C(sp3)−H bond in the starting substance by the photo‐excited aryl ketone. The derived carbon radical was then promptly trapped by TEMPO leading to the formation of the TEMPO‐adduct. The derived TEMPO‐adduct is synthetically versatile as an alcohol equivalent since it can be readily converted to the corresponding ketone by oxidation and to the corresponding alcohol by reduction. The key to realizing the present catalytic reaction relies on the distinctive triple role of TEMPO, which acts as the precursor of the oxygen functionality, the oxidant to regenerate the aryl ketone, and the protective group for the derived TEMPO‐adduct from over‐oxidation. [ABSTRACT FROM AUTHOR]

A Cu(I)‐catalyzed [4+2] oxidative annulation of α,β‐unsaturated ketoxime acetates with cyclopropanols has been developed for the synthesis of 2,4,5‐trisubstituted pyridines in 28–76% yields. This method employs cyclopropanols as C2 synthons and features various functional group compatibility and gram‐scale synthesis. In addition, a plausible reaction pathway was proposed based on the mechanism studies. [ABSTRACT FROM AUTHOR]

A feasible and umpolung strategy for the synthesis of structurally diverse β-amino ketones has been achieved through TEMPO mediated C-N coupling of cyclopropanols with nitrogen nucleophiles. Mechanism studies indicated that in situ generated enones derived from cyclopropanols are the key intermediates and TEMPO play multiple roles, including radical initiator, trapping reagent, a porter of β-hydrogen and an in situ base. This protocol features broad substrate scope, good scalability and good to excellent yields and provides an alternative and complementary approach to the synthesis of structurally important β-amino ketone scaffolds under metal and additive-free conditions. [ABSTRACT FROM AUTHOR]

Modification of amino acids is an important strategy in organic and bioorganic chemistry. In contrast to common side‐chain functionalization, backbone modification is much less explored. Especially glycine units seem to be attractive and versatile since a wide range of functionality can be potentially introduced. We report here oxidative modification of glycinates that are stable and enable further functionalization. Selective glycinate enolate oxidation by TEMPO or a FeCp2PF6/TEMPO reagent combination provides stable alkoxyamines in good to excellent yields. The methodology is expanded to glycine‐containing dipeptides demonstrating selective oxygenation at the glycine unit. The orthogonal reactivity potential of oxygenated glycines for transformation to other amino acid derivatives is explored. [ABSTRACT FROM AUTHOR]

An approach to the vicinal oxyazidation of alkenes has been achieved under mild and transition metal-free conditions. This method utilizes NaN3 as the azidation agent and 2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (TEMPO+BF4-) as the single-electron oxidant as well as the oxygen source. By using this protocol, various ß-aminooxy azides were synthesized and several complex bioactive molecules were functionalized. [ABSTRACT FROM AUTHOR]

We report a TEMPO‐mediated oxidative copper‐catalyzed synthesis of N‐(fluoroalkyl)imidazolones via the radical addition of imidazoles with iodofluoroacetate. A possible key intermediate involving TEMPO was observed by ESI‐MS. We also found that aerobic oxidation conditions were effective for the transformation in the presence of a copper catalyst, enabling access to a number of N‐(fluoroalkyl)imidazolones in moderate to good yields. [ABSTRACT FROM AUTHOR]

In this study we describe the reactivity of unsaturated N‐alkoxyureas in the presence of different combinations of a hypervalent iodine(III) reagent and a bromide source or TEMPO. Three complementary cyclizations can be achieved depending on the reaction conditions. On the one hand, PIFA with pyridinium bromide leads to an oxybromination reaction. On the other hand, bis(tert‐butylcarbonyloxy)iodobenzene with tetrabutylammonium bromide or TEMPO triggers aminobromination or aminooxyamination reactions, respectively. Control experiments showed that the three reactions proceed through distinct mechanisms: the first process is ionic while the other two follow a radical manifold. [ABSTRACT FROM AUTHOR]

A novel oxidative cascade cyclization of α‐[(β‐amino)propenoyl]‐alkylamides mediated by phenyl iodine (III) bis(trifluoroacetate) (PIFA) and 2,2,6,6‐tetramethyl piperidin‐1‐oxyl (TEMPO) has been described. This unprecedented transformation features mild reaction conditions, simple execution, high chemo‐ and regio‐selectivity, and thereby provides a facile and efficient protocol for the synthesis of polysubstituted 3,7‐dihydro‐ oxazolo[4,5‐c]pyridine‐2,4,6‐(5 H)‐triones. [ABSTRACT FROM AUTHOR]

A novel method for the synthesis of cyanomethylated tetrahydroisoquinolines has been developed with mild reaction conditions, good yields and a broad substrate scope. Acetonitrile, a common solvent, is for the first time used as a pronucleophile for this type of two sp3 C−H bonds cross-dehydrogenative coupling (CDC) reaction. A new oxidative system (CuCl2/TEMPO/Cs2CO3) has been established by our group, in which the mild TEMPO reagent was found to be a highly efficient oxidant. [ABSTRACT FROM AUTHOR]

A novel fullerene [5:1]hexakisadduct bearing two 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) radicals and ten 1-propyl-3-methylimidazolium bromide moieties has been synthesized and characterized. Such an C60IL10TEMPO2 hybrid has been successfully employed as a catalyst in the selective oxidation of a wide series of alcohols and is highly active at just 0.1 mol% loading. Moreover, it can be easily recovered by adsorption onto a multi-layered covalently-linked SILP phase (mlc-SILP) through a 'release and catch' approach and reused for up to 12 cycles without loss in efficiency. Interestingly, a catalytic synergistic effect of TEMPO and imidazolium bromide moieties combined in the same hybrid has been clearly shown. [ABSTRACT FROM AUTHOR]

The reactivity of homogeneous copper catalysts towards the selective CC bond cleavage of both phenolic and non-phenolic arylglycerol β-aryl ether lignin model compounds has been explored. Several copper precursors, nitrogen ligands, and solvents were evaluated in order to optimize the catalyst system. Using the optimized catalyst system, copper(I) trifluoromethanesulfonate [Cu(OTf)]/L/TEMPO (L=2,6-lutidine, TEMPO=2,2,6,6-tetramethyl-piperidin-1-yl-oxyl), aerobic oxidation of the non-phenolic β-O-4 lignin model compound proceeded with good selectivity for CαCβ bond cleavage, affording 3,5-dimethoxybenzaldehyde as the major product. Aerobic oxidation of the corresponding phenolic β-O-4 lignin model proceeded with different selectivity, affording 2,6-dimethoxybenzoquinone and α,β-unsaturated aldehyde products resulting from cleavage of the CαCaryl bond. At low catalyst concentrations, however, a change in selectivity was observed as oxidation of the benzylic secondary alcohol predominated with both substrates. [ABSTRACT FROM AUTHOR]

An efficient copper-catalyzed α-aminoxylation of ketones with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) is presented for the synthesis of 2-aryloxy-1-aryl-2-(2,2,6,6-tetramethylpiperidin-1-yloxy)ethanones in moderate to excellent yields. It is noteworthy that the copper/iron (Cu/Fe) catalyst can be recovered and reused several times with high catalytic reactivity. [ABSTRACT FROM AUTHOR]

An efficient catalytic system to oxidize quantitatively aliphatic diols using Trametes versicolor laccase and TEMPO has been developed in aqueous medium. Oxidations have occurred in a non-stereoselective fashion but with complete regio- and/or monoselectivity, obtaining lactones with excellent purity after simple extraction. This catalytic system has been demonstrated to be scalable, compatible with the presence of a variety of functionalities, and also allowed the successful enzyme recycling using a laccase-cross-linked enzyme aggregates (CLEA) preparation. [ABSTRACT FROM AUTHOR]