Unexpected rearrangements and a novel synthesis of 1,1-dichloro-1-alkenones from 1,1,1-trifluoroalkanones with aluminium trichloride

Insights into the Mechanism of Aluminum-Catalyzed Halodefluorination

Aluminum has been reported to catalyze halodefluorination reactions, where aliphatic fluorine is substituted with a heavier halogen. Although it is known that stoichiometric aluminum halide can perform this reaction, the role of catalytic aluminum halide and organyl alane reagents is not well understood. We investigate the mechanism of the halodefluorination reaction using catalytic aluminum halide and stoichiometric trimethylsilyl halide. We explore the use of B(C₆F₅)₃ as a catalyst to benchmark pathways where aluminum acts either as a Lewis acid catalyst in cooperation with trimethylsilyl halide or as an independent halodefluorination reagent which is subsequently regenerated by trimethylsilyl halide. Computational and experimental results indicate that aluminum acts as an independent halodefluorination reagent and that reactivity trends observed between different halide reagents can be attributed to relative barriers in halide delivery to the organic fragment, which is the rate-limiting step in both the aluminum halide- and B(C₆F₅)₃-catalyzed pathways.

Theoretical Investigation of para Amino-Dichloro Chalcone Isomers. Part II: A DFT Structure-Stability Study of the FMO and NLO Properties

The density functional theory (DFT) method using the functional hybrid (B3LYP) and 6-311G(d,p) basis set was utilized for the geometry optimization with dispersion correction, procedure (GO + DC), for the E and Z chalcone isomers -1-(4-aminophenyl)- 3-(i,j-dichlorophenyl)prop-2-en-1-one, where (i) and (j) represent the positions of the two chlorine atoms [(2,3), (2,4),(2,5),(2,6),(3,4), and (3,5)] abbreviated (i,j)-chalcone, and 4-(x,y-dichloro-8aH-chromen-2-yl)aniline, where (x = 5,6 and y = 6,7,8,8a) abbreviated (x,y)-chromen isomers. The calculations revealed that E chalcones are the most stable and the 4-(x,y-dichloro-8aH-chromen-2-yl) aniline isomers are the least stable. The (3,5) chalcones were the most stable in both E and Z chalcone series. However, the 4-(5,8a-dichloro-8aH-chromen-2-yl) aniline is the most stable in the series. The isomer stability order is the same as in Part 1, in which the geometry optimization calculation was followed by the dispersion correction single point energy calculation (GO/SPDC) procedure. The procedures (GO + DC) and (GO/SPDC) were used to calculate energies of the highest occupied molecular orbital (HOMO) and lowest-unoccupied molecular orbital (LUMO) and related properties. The order of the HOMO-LUMO energy gap (ΔE gap) was chromens Collapse

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Affiliation(s)

Haval A. Hussein Department of Chemistry, College of Science, University of Duhok, Zakho Street 38, 1006AJDuhok, Kurdistan Region, Iraq
Ghazwan F. Fadhil Department of Chemistry, College of Science, University of Duhok, Zakho Street 38, 1006AJDuhok, Kurdistan Region, Iraq

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Activation of C-Br Bond of CBr4 and CBrCl3 Using 9-Mesityl-10-methylacridinium Perchlorate Photocatalyst

Herein, we report the activation of the C-Br bond of CBrX₃ (X = Cl, Br) using 9-mesityl-10-methylacridinium perchlorate as a visible-light (12W blue LED, 450-455 nm) photocatalyst for the synthesis of gem-dihaloenones from terminal alkynes. An electron transfer from CBrX₃ to Mes-Acr-MeClO₄ led to the formation of ^•+CBrX₃ which subsequently resulted in the intermediate ⁺CX₃. Next, C-C cross-coupling of ⁺CX₃ with terminal alkynes was the key path to obtain the gem-dihaloenones. Radical trapping experiments with TEMPO, BHT, and Stern-Volmer quenching studies helped to understand that the reaction proceeded via the SET mechanism.

A Review on the Halodefluorination of Aliphatic Fluorides

Halodefluorination of alkyl fluorides using group 13 metal halides has been known for quite some time (first reported by Newman in 1938) and is often utilized in its crude stoichiometric form to substitute fluorine with heavier halogens. However, recently halodefluorination has undergone many developments. The reaction can be effected with a range of metal halide sources (including s-block, f-block, and p-block metals), and has been developed into a catalytic process. Furthermore, methods for monoselective halodefluorination in polyfluorocarbons have been developed, allowing exchange of only a single fluorine with a heavier halogen. The reaction has also found use in cascade processes, where the final product may not even contain a halide, but where the conversion of fluorine to a more reactive halogen is a pivotal reaction step in the cascade. This review provides a summary of the developments in the reaction from its inception until now.

1 Introduction

2 Stoichiometric Halodefluorination

2.1 Group 13 Halodefluorination Reagents

2.2 Other Metal Halide Mediated Halodefluorination

3 Catalytic Halodefluorination

4 Monoselective Halodefluorination

5 Cascade Reactions Involving Halodefluorination

6 Summary and Outlook