Di-tert-butyl peroxide (DTBP)
Di-tert-butyl peroxide is a very stable organic peroxide, that is often used a radical initiator, as it performs homolysis at temperatures above 100°C.
In the presence of a catalytic amount of copper(II) acetate and di-tert-butyl peroxide, a cross-coupling reaction of anilines with alkylborane reagents gives N-alkylated anilines in good to excellent yields. Phenols are also applicable for this reaction.
S. Sueki, Y. Kuninobu, Org. Lett., 2013, 15, 1544-1547.
The key to the success of a general catalytic procedure for the cross-coupling of primary amides and alkylboronic acids was the identification of a mild base (NaOSiMe3) and oxidant (di-tert-butyl peroxide) to promote the copper-catalyzed reaction in high yield. This transformation provides a facile, high-yielding method for the monoalkylation of amides.
S. A. Rossi, K. W. Shimkin, Q. Xu, L. M. Mori-Quiroz, D. A. Watson, Org. Lett., 2013, 15, 2314-2317.
An efficient copper-catalyzed amidation of benzylic hydrocarbons and inactive aliphatic alkanes with simple amides proceeded smoothly without any ligand. A wide range of N-alkylated aromatic and aliphatic amides, sulfonamides, and imides were synthesized in good yields.
H.-T. Zeng, J.-M. Huang, Org. Lett., 2015, 17, 4276-4279.
The use of DTBP as radical initiator and a copper salt as promoter enables the preparation of allylic alcohol, benzyl, and alkane derivatives via a radical mechanism. The C(sp3)-H bond in various alcohols, toluene derivatives, and alkanes were successfully alkenylated with β-nitrostyrenes to yield the desired products in good yields.
S.-r. Guo, Y.-q. Yuan, Synlett, 2015, 26, 1961-1968.
An efficient method enables the synthesis of α-cyanomethyl-β-dicarbonyls in good yields from MeCN and simple 1,3-dicarbonyls. A radical mechanism is proposed.
C. Wang, Y. Li, M. Gong, Q. Wu, J. Zhang, J. K. Kim, M. Huang, Y. Wu, Org. Lett., 2016, 18, 4151-4153.
An efficient coupling of arylboronic acids with dimethyldisulfide under metal-free conditions provides aryl methyl sulfides. The method offers operational simplicity, satisfactory yields, excellent functional-group tolerance, as well as mild reaction conditions.
X.-m. Wu, J.-m. Lou, G.-b. Yan, Synlett, 2016, 27, 2269-2273.
Copper(I) salts catalyze a synthesis of multisubstituted furans from readily available acetophenones and electron-deficient alkynes via direct C(sp3)-H bond functionalization under radical reaction conditions in the presence of di-tert-butyl peroxide as an external oxidant. This method offers an efficient access to biologically important scaffolds from simple compounds.
S. Manna, A. P. Antonchick, Org. Lett., 2015, 17, 4300-4303.
A radical-promoted cross-dehydrogenative coupling strategy enables a metal- and base-free one-pot synthesis of 2,5-diaryl 1,3,4-oxadiazoles via N-acylation of aryl tetrazoles with aryl aldehydes, followed by thermal rearrangement. A broad range of aryl tetrazoles and aryl aldehydes deliver the corresponding products in good yields.
L. Wang, J. Cao, Q. Chen, M. He, J. Org. Chem., 2015, 80, 4743-4748.
A copper-catalyzed sp3 C-H functionalization of 2-alkyl-N-substituted benzamides provides an efficient approach to various functionalized isoindolinones without preparation of halogenated substitutes, use of expensive transition metals, or toxic Sn or CO gas.
K. Nozawa-Kumada, J. Kadokawa, T. Kameyama, Y. Kondo, Org. Lett., 2015, 17, 4479-4481.
Iodine-catalyzed cascade reactions of substituted thiophenols with alkynes under metal- and solvent-free conditions enable the synthesis of benzothiophene derivatives in good yields. Such an efficient, economical, and green transformation should provide an attractive approach to various benzothiophenes.
K. Yan, S. Yang, M. Zhang, W. Wei, Y. Liu, L. Tian, H. Wang, Synlett, 2015, 26, 1890-1894.
Copper-catalyzed C-H bond activation enables a facile, efficient, and simple protocol for direct oxidative C-H amination of benzoxazoles with primary amines using tert-butyl peroxide (TBP) as oxidant under air. Various substituted aminobenzoxazoles were synthesized with very good yields.
J. Gu, C. Cai, Synlett, 2015, 26, 639-642.
A copper/iodine cocatalyzed decarboxylative cyclization of α-amino acids with either 2-benzoylpyridines or 2-benzoylquinolines provides 1,3-disubstituted imidazo[1,5-a]pyridines and 1,3-disubstituted imidazo[1,5-a]quinolines in excellent yields.
H. Wang, W. Xu, L. Xin, W. Liu, Z. Wang, K. Xu, J. Org. Chem., 2016, 81, 3681-3687.