PMID- 34368526
OWN - NLM
STAT- PubMed-not-MEDLINE
LR  - 20210810
IS  - 2470-1343 (Electronic)
IS  - 2470-1343 (Linking)
VI  - 6
IP  - 30
DP  - 2021 Aug 3
TI  - Effect of Novel Deep Eutectic Solvents on the Endo/Exo Ratio of Diels-Alder 
      Reactions at Room Temperature.
PG  - 19392-19399
LID - 10.1021/acsomega.1c00980 [doi]
AB  - The Diels-Alder reaction is a prototypical example of a thermally allowed [4 + 2] 
      cycloaddition with good control over the regio- and stereochemical outcomes. 
      Therefore, Diels-Alder reactions in which adjacent stereocenters are generated at 
      the two ends of the newly formed single bonds imply two different possible 
      stereochemical outcomes. In cases where the dienophile has a single 
      electron-withdrawing substituent, the outcome can often be predicted by applying 
      the known "endo rule". Furthermore, the use of chiral eutectic solvents in 
      asymmetric synthesis has become a novel tool to maintain sustainability in 
      organic synthesis. In the present work, a set of recyclable and sustainable 
      bio-based deep eutectic solvents (DESs) was designed using hydrogen bond 
      acceptors (HBAs) with a chiral center. These compounds were used in their racemic 
      and enantiomerically enriched forms to prepare DESs with lactic acid (LA), 
      glycerol (Gly), and ethylene glycol, which act as hydrogen bond donors (HBDs) in 
      the corresponding eutectic mixture. These DESs were used as solvents to study the 
      reaction between cyclopentadiene and ethyl acrylate or butyl acrylate in typical 
      [4 + 2] cycloadditions. The best yields and endo-selectivity were achieved using 
      LA as the HBD in the eutectic mixtures. The results and adduct ratios obtained 
      show that these DESs were able to improve both reaction yields and selectivity 
      when compared to those observed in organic solvents or ionic liquids. Moreover, 
      the reaction products (adducts) were easily recovered with diethyl ether from the 
      reaction mixture, where they appeared as an upper layer.
CI  - (c) 2021 The Authors. Published by American Chemical Society.
FAU - Torres, Paulo
AU  - Torres P
AD  - Department of Chemistry-DBA Center, University of Lleida, ETSEA, Av. Rovira Roure 
      191, 25198 Lleida, Catalonia, Spain.
FAU - Balcells, Merce
AU  - Balcells M
AD  - Department of Chemistry-DBA Center, University of Lleida, ETSEA, Av. Rovira Roure 
      191, 25198 Lleida, Catalonia, Spain.
FAU - Canela-Garayoa, Ramon
AU  - Canela-Garayoa R
AUID- ORCID: 0000-0003-1095-6607
AD  - Department of Chemistry-DBA Center, University of Lleida, ETSEA, Av. Rovira Roure 
      191, 25198 Lleida, Catalonia, Spain.
LA  - eng
PT  - Journal Article
DEP - 20210722
PL  - United States
TA  - ACS Omega
JT  - ACS omega
JID - 101691658
PMC - PMC8340089
COIS- The authors declare no competing financial interest.
EDAT- 2021/08/10 06:00
MHDA- 2021/08/10 06:01
PMCR- 2021/07/22
CRDT- 2021/08/09 06:46
PHST- 2021/02/23 00:00 [received]
PHST- 2021/05/31 00:00 [accepted]
PHST- 2021/08/09 06:46 [entrez]
PHST- 2021/08/10 06:00 [pubmed]
PHST- 2021/08/10 06:01 [medline]
PHST- 2021/07/22 00:00 [pmc-release]
AID - 10.1021/acsomega.1c00980 [doi]
PST - epublish
SO  - ACS Omega. 2021 Jul 22;6(30):19392-19399. doi: 10.1021/acsomega.1c00980. 
      eCollection 2021 Aug 3.