A general method for the regioselective synthesis of a series of ortho-substituted chrysenyl N, N-diethyl- O-carbamates by the directed ortho-metalation (D oM) strategy is reported. The starting O-carbamates were prepared from the corresponding chrysenols, available by oxidative photochemical cyclization or directed remote metalation tactics. Chrysen-1-yl and chrysene-3-yl ring site selectivity of directed ortho-metalation (D oM) and anionic ortho-Fries rearrangement (A oF) protocols, with s-BuLi/TMEDA, followed by electrophilic quench using a selection of electrophiles, were observed, leading to new chrysenyl derivatives. 5-Chrysenyl N,N-diethyl- O-carbamate underwent instant A oF rearrangement even at -100 °C to furnish chrysenyl o-hydroxycarboxamide. Iterative D oM reactions were carried out to gain insight into the regioselectivity factors.
Comparative developmental toxicity at the limit of solubility appears unrelated to the position of alkyl substitution. Toxic effects are like crude oil exposures, however much higher doses of the individual compounds are needed.
Polycyclic aromatic
hydrocarbons (PAHs) with six and seven rings
were synthesized
via
directed metalation and cross-coupling
of chrysenyl
N
,
N
-diethyl carboxamides
with
o
-tolyl and methylnaphthalenyl derivatives.
In the presence of competing
ortho
sites, the site
selectivity in iodination of chrysenyl amides by directed
ortho
metalation (D
o
M) was influenced by
the lithium base. The catalyst ligand bite angle was presumably important
in the cross-coupling of sterically hindered bulky PAHs. Subsequent
directed remote metalation of biaryls under standard conditions and
at elevated temperatures afforded various fused six- and seven-ring
PAHs, all in good yields and with fluorescent properties.
New polycyclic hexahydrobenzo[c]acridines were synthesized in excellent yields by intramolecular [4+2]-cycloaddition reactions of aldimines derived from aromatic amines and 2-(4-methylpent-3-en-1-yl)benzaldehyde in acetonitrile in the presence of 10 mol% of bismuth(III) chloride. The reaction is highly diastereoselective, giving cisfused benzoacridine derivatives preferentially.
Over the past decades, organic chemists have focussed on developing new approaches to directed C–H functionalisations, where the site selectivity is steered by the presence of a directing group (DG). Nonetheless, in recent years, more and more non-directed strategies are being developed to circumvent the requisite directing group, making C–H functionalisations more generic. This short review focuses on the latest developments in palladium-catalysed non-directed C–H functionalisations of aromatic compounds.1 Introduction2 C–C Bond Formation2.1 C–H Arylation2.2 C–H Alkylation2.3 C–H Alkenylation2.4 C–H Carbonylation3 C–Heteroatom Bond Formation3.1 C–O Bond Formation3.2 C–N Bond Formation3.3 C–S Bond Formation4 Conclusion
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