4 research outputs found
N‑Alkylated 1,4-Diazabicyclo[2.2.2]octane–Polyethylene Glycol Melt as Deep Eutectic Solvent for the Synthesis of Fisher Indoles and 1<i>H</i>‑Tetrazoles
No full text1,4-DiazabicycloÂ[2.2.2]Âoctane
(DABCO)-based ionic liquids (ILs) <b>2–4</b> were synthesized
by the N-alkylation of DABCO using
alkyl halides of varying chain lengths (C<sub>2</sub>, C<sub>5</sub>, and C<sub>7</sub>). The N-alkylated DABCO-ILs were mixed with polyethylene
glycols (PEGs) of varying molar masses as hydrogen bond donors (HBDs)
to prepare new deep eutectic solvents (DESs). These DABCO–PEG-based
DESs were successfully employed for the synthesis of a variety of
indoles <b>7a–7h</b> (by Fischer indole synthesis) and
1<i>H</i>-tetrazoles <b>9a–9i</b> (by click
chemistry). For comparison, DESs of DABCO-ILs with different alcohols
(as HBD) were also prepared and investigated for the synthesis of
indoles. Although comparable yields were observed in DES-containing
alcohols and PEGs, the use of PEG as HBD in DES (as an alternative
to alcohols) provides a much safer, nonvolatile, and environmentally
benign reaction medium for synthetic reactions. The first successful
application of PEG-polymer-based DES as benign reaction media for
organic syntheses offers exciting opportunities to be explored in
the realm of green synthesis
