85208-90-8Relevant academic research and scientific papers
Thiazolium carbene catalysts for the fixation of CO2 onto amines
Das, Shoubhik,Bobbink, Felix D.,Bulut, Safak,Soudani, Mylène,Dyson, Paul J.
supporting information, p. 2497 - 2500 (2016/02/18)
The catalytic N-formylation and N-methylation of amines using CO2 as the carbon source represents a facile and sustainable approach for the synthesis of pharmaceuticals and natural products. Herein, we describe highly effective and inexpensive thiazolium carbene-based catalysts derived from vitamin B1 for the N-formylation and N-methylation of amines, using polymethylhydrosiloxane (PMHS) as a reducing agent, which operate under ambient conditions.
Transesterifications with 1,8-Diazabicycloundec-7-ene/Lithium Bromide (DBU/LiBr) - Also Applicable to Cleavage of Peptides from Resins in Merrifield Syntheses
Seebach, Dieter,Thaler, Adrian,Blaser, Denis,Ko, Soo Y.
, p. 1102 - 1118 (2007/10/02)
A mixture of the amidine base 1,8-diazabicycloundec-7-ene (DBU) and LiBr (preferably 0.5 and 5 equiv., resp.) turns out to be a highly efficient catalyst (at 0-25 deg C) for saponifications (in THF/H2O) and transesterifications (in ROH).The scope and limitations of the method are determined using ca. two dozens of different ester/alcohol combinations (Schemes 2 and 3).The investigation is focused on peptides as substrates.Under carefully controlled conditions, no epimerization occurs with N-Boc- and N-Z-protected peptide esters, when methyl, ethyl, isopropyl, or allyl esters are the products, as shown for peptides containing up to six amino acids, with Ala, Leu, MeLeu, Asp(OEt), or Tyr at the C-terminus (Scheme 3 and Tables 1 and 2).Hydrolytic and transesterifying detachments of Boc-Leu-Ala-Gly-Val-OR and Boc-Leu-Ala-Gly-Phe-OR (R = H, Me) from PAM and Wang resins (1-8 h at 0-25 deg C, 2 equiv. of DBU, 5 equiv. of LiBr) can be achieved by this method without epimerization of the C-terminal stereogenic center; a comparison with other methods (HF, Ti(OR)4) is given (Schemes 4 and 5).Possible protecting-group strategies involving the DBU/LiBr method are discussed (Table 3).Extensive experimental details are given.
