Cobalt‐Catalyzed Alkylation–Peroxidation of Alkenes with 1,3‐Dicarbonyl Compounds and T‐Hydro

Abstract

Am ethod for the cobalt-catalyzed alkylation-peroxidation of alkenes with 1,3-dicarbonyl compounds and Thydro (tert-butyl hydroperoxide solution) was developed. This approachp rovides practical and selective access to g-carbonyl peroxides in as ingles tep by startingf rom readily availables tarting materials. In addition, gram-scale syntheses demonstrated that the protocol is practical and useful for organic synthesis. Scheme1.Synthetic strategies for a-CÀHf unctionalization of carbonyl compounds (E = electrophile, M = metal,Ln= ligand, FG = functional group).Scheme2.Alkylation-peroxidation of alkenes.[a] S.GeneralP rocedure for Synthesis of 5:T oadry Schlenk tube were added 2-[2-(tert-butylperoxy)-2-phenylethyl]-1,3-diphenylpropane-1,3-dione (3a,0 .2 mmol), amine 4 (0.24 mmol), and anhydrous MeCN (1.0 mL) at room temperature. Then, TfOH (0.2 mmol) was added to the solution, and the resulting mixture was stirred at 85 8Cf or 1h.A fter cooling the mixture to room temperature, the solvent was evaporated under vacuum. The residue was purified by flash column chromatography on silica gel (ethyl acetate/ petroleum ether)t ogive product 5.

Cobalt(II) Complexes with N,N,N-Scorpionates and Bidentate Ligands: Comparison of Hydrotris(3,5-dimethylpyrazol-1-yl)borate Tp* vs. Phenyltris(4,4-dimethyloxazolin-2-yl)borate ToM to Control the Structural Properties and Reactivities of Cobalt Centers

“…To date, some cobalt compounds, including Tp R [ 27 , 28 ] and To M [ 10 ] complexes, have been employed as catalysts for hydrocarbon oxygenation with organic peroxides (ROOH) such as tert -butyl hydroperoxide (TBHP) [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ] and meta -chloroperbenzoic acid ( m CPBA) [ 10 , 37 , 38 , 39 , 40 , 41 , 42 , 43 ]. Therefore, we explored catalysis of the entitled mixed ligand complexes toward alkene oxidation with TBHP and alkane oxidation with m CPBA as indicated below.…”

“…Products derived from the allylic oxidation are allylic alcohol ( A ), ketone ( K ), and peroxide ( P ). Formation of P indicates involvement of alkylperoxyl radical ( tert -BuOO·), which is formed by degradation of TBHP through the Habor–Weiss mechanism and/or homolysis of an M–O bond of a putative metal–alkylperoxo complex [ 36 , 44 ]. In our previous work, catalytic activity of the cobalt(II) compounds, including a genuine cobalt(II) acetate, tetrahedral cobalt(II) complex [Co II Br(allyl-Tp CF3 )] (allyl-Tp CF3 denotes allyltris(3-trifluoromethyl-1-pyrazol-1-yl)borate), and mesoporous silica-supported Tp CF3 Co complexes, was examined without any additive, and the activity of Co II (OAc) 2 ·4H 2 O and [Co II Br(allyl-Tp CF3 )] under homogeneous conditions was lower than that of the immobilized complexes under heterogeneous reactions [ 28 ].…”

Benzannulation of Pyrroles to 4,5‐Disubstituted Indoles through Brønsted‐Acid‐Promoted Rearrangement of tert‐Butyl Peroxides

“…γ‐Carbonyl tert ‐butyl peroxides 11 could be prepared by cobalt‐catalyzed alkylation–peroxidation of alkenes with 1,3‐dicarbonyl compounds and T‐hydro (70 % tert ‐butyl hydroperoxide in water) in gram scale with good yields . We previously reported the use of these peroxides as diene precursors in the synthesis of carbazoles by benzannulation of indoles through an acid‐catalyzed rearrangement of 11 .…”

“…All chemical reagents were purchased from Alfa Aesar, Acros, Sigma–Aldrich, TCI, or J&K and used without further purification. Compounds 11 were prepared according to our previous work . Pyrroles 12 b – g , 12 h and 12 i , 12 j , 12 k , and 12 l were prepared according to literature reports.…”

Three-component reactions of aromatic amines, 1,3-dicarbonyl compounds, and α-bromoacetaldehyde acetal to access N-(hetero)aryl-4,5-unsubstituted pyrroles

“…α,β-Unsaturated aldehydes have also been used as the C 3 donor to construct pyrrole scaffolds [27,28]; (ii) [1 + 4] annulation, in which (hetero)arylamines are reacted with a C 4 donor to form the pyrrole ring; many functional molecules, such as bioderived furans [29], (Z)-enynols [30], 1-vinylpropargyl alcohols [31], doubly activated cyclopropanes [32], and enynals [33], can be used as C 4 counter reagents. The carbon-based 1,4-biselectrophiles, such as the 1,4-dicarbonyl compounds [34,35], γ-car-bonyl tert-butyl peroxides [36], and dihydrofurans [37] have also been reported to construct the pyrrole skeletons through this type of annulation; and (iii) [1 + 2 + 2] annulation, in which (hetero)arylamines are reacted with two different molecules, and each of them contributes two carbon atoms to construct a pyrrole ring [38][39][40][41][42]. Among these three approaches, the third is considered the most attractive route for N-(hetero)aryl-4,5-unsubstituted pyrrole synthesis.…”