“…[22][23][24][25][26][27] Products such us propylene glycols are used for the synthesis of polyester resins, liquid detergents, drugs and cosmetics. [28][29][30][31][32] Glycerol can also be converted into branched oxygen-containing components by catalytic etherification with alcohols or alkenes. [33][34][35][36][37] It can be dehydrated to glycidol 38,39 and used for the production of 1,3-propanediol via biotechnology.…”
Multifunctional monomers based on glycerol carbonate are employed in the chemical industry for the production of polyurethanes and polycarbonates. To avoid the use of toxic phosgene as carboxylating reagent, eco-friendly routes have been developed using alternative agents. In this paper, a series of binary and ternary oxides have been tested as catalysts in the synthesis of diglycerolether dicarbonate (DGDC) and diglycerol tricarbonate (DGTC) using dimethyl carbonate (DMC) and urea as carboxylating agents. The recovery and reuse of the catalysts are discussed. In the best reaction conditions, using mixed oxides La:Ca = 1:1 as catalysts, the yields of DGDC and DGTC were >90 (pure isolated compounds) and 19.9%, respectively
“…[22][23][24][25][26][27] Products such us propylene glycols are used for the synthesis of polyester resins, liquid detergents, drugs and cosmetics. [28][29][30][31][32] Glycerol can also be converted into branched oxygen-containing components by catalytic etherification with alcohols or alkenes. [33][34][35][36][37] It can be dehydrated to glycidol 38,39 and used for the production of 1,3-propanediol via biotechnology.…”
Multifunctional monomers based on glycerol carbonate are employed in the chemical industry for the production of polyurethanes and polycarbonates. To avoid the use of toxic phosgene as carboxylating reagent, eco-friendly routes have been developed using alternative agents. In this paper, a series of binary and ternary oxides have been tested as catalysts in the synthesis of diglycerolether dicarbonate (DGDC) and diglycerol tricarbonate (DGTC) using dimethyl carbonate (DMC) and urea as carboxylating agents. The recovery and reuse of the catalysts are discussed. In the best reaction conditions, using mixed oxides La:Ca = 1:1 as catalysts, the yields of DGDC and DGTC were >90 (pure isolated compounds) and 19.9%, respectively
“…Since the (2 S, 3 R ) enantiomer is more conveniently transformed into thiamphenicol, the ee's obtained for acid 4 are too low to be of practical use. Furthermore a reverse enantioselectivity in this kinetic resolution process would be much more advantageous; the remaining ester 7 then could be obtained in high ee while the enantiomerically enriched acid 4 could be racemized 5b. Because further processing to thiamphenicol proceeds via the ester, additional steps would then not be required.…”
Section: Resultsmentioning
confidence: 99%
“…No efforts at optimization and scale-up of this reaction were made (Scheme ). The enantiopure (1 R, 2 R ) amino diol 3 , obtained in 73% yield from 4 , can be transferred into thiamphenicol and florfenicol by methods described in the literature. − 8 …”
Section: Resultsmentioning
confidence: 99%
“…In practice two routes are used for the resolution: classical resolution of the threo -3-[4-(methylsulfonyl)phenyl]serine ethyl ester ( 2 ) using tartaric acid as a resolving agent and resolution by preferential crystallization of threo -2-amino-1-[4-(methylthio)phenyl]propane-1,3-diol ( 3 ) . However, as a consequence of both resolution methods the undesired enantiomer remains as waste, though for both methods laborious racamization protocols for the undesired enantiomer are described . Late in the resolution process, an elegant solution is described for the amino diol 3 by Giordano et al, who developed a process based on the inversion of both chiral centers of (1 S, 2 S )- 3 yielding the required (1 R, 2 R ) enantiomer.…”
Enantiomerically pure 4-methylthio- and 4-methylsulfonyl-substituted (2S,3R)-3-phenylserines are prepared
by enzymatic
resolution of the corresponding racemic threo amides using
the
amidase from Ochrobactrum anthropi NCIMB 40321.
The
unwanted (2R,3S) enantiomers of the amides are
separated from
the enantiopure amino acids and easily racemized after
Schiff
base formation with the corresponding 4-(methylthio)- and
4-(methylsulfonyl)benzaldehyde. The racemization can
be
combined with the preparation of the racemic amides by
aldol
reaction under crystallization conditions to yield only the
threo
isomers. Enantiopure
(2S,3R)-3-[4-(methylthio)phenyl]serine
and
(2S,3R)-3-[4-(methylsulfonyl)phenyl]serine
are thus obtained in 78% and 62% overall yields starting from the
corresponding substituted benzaldehydes.
(2S,3R)-3-[4-(Methylthio)phenyl]serine is reduced to
(1R,2R)-2-amino-1-[4-(methylthio)phenyl]propane-1,3-diol with
NaBH4/H2SO4 and can
be
used for the synthesis of thiamphenicol and florfenicol.
“…Others are one-pot reaction of the amino alcohol with the 2-halogenobenzonitrile catalyzed with ZnCl2 (Scheme 1, Method 2) [15] and condensation with an imidate (Scheme 1, Method 3). The halogenophenyloxazolines are also synthesize in three steps synthesis (Scheme 2) involving formation of an amide, in the first step, and next transformation of the hydroxyl group into a leaving group Cl (Scheme 2, Method 4) or OTs (Scheme 2, Method 5) [16] followed by the ring closure or direct cyclization in presence of Bu2SnCl2 (Scheme 2, Method 6) [17]. The last step in the PHOX ligands construction is substitution of a halogen atom by the phosphino group (Scheme 3, Method 7 and 8).…”
In this paper we present synthesis new PHOX ligands α-and β-pinene derivatives. We applied their ruthenium (I) complexes in asymmetric catalytic transfer hydrogenation of ketones with good yields and enantioselectivity.
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