- A new method for the lactonization of ω-hydroxy carboxylic acids with Di-2-thienyl carbonate by the promotion of DMAP and iodine
-
Successive reactions of ω-hydroxycarboxylic acids with an equimolar amount of di-2-thienyl carbonate (2-DTC) in the presence of a catalytic amount of 4-(dimethylamino)pyridine (DMAP) followed by an addition of 2-4 equimolar amounts of iodine afforded the corresponding lactones in good to high yields. Copyright
- Oohashi, Yoshiaki,Fukumoto, Kentarou,Mukaiyama, Teruaki
-
-
- A new method for the synthesis of carboxylic esters and lactones with di-2-thienyl carbonate (2-DTC) by the promotion of DMAP and iodine
-
The esterification of carboxylic acids with alcohols by using di-2-thienyl carbonate (2-DTC) in the presence of a catalytic amount of 4-(dimethylamino) pyridine (DMAP) proceeded smoothly to afford the corresponding esters in good-to-high yields along with 2(5H)-thiophenone. This esterification was accelerated by the addition of an equimolar amount of iodine to afford the esters in higher yields within a shorter reaction time. Further, cyclization of ω-hydroxycarboxylic acids with an equimolar amount of 2-DTC in the presence of a catalytic amount of DMAP, followed by the addition of 1-4 equimolar amounts of iodine, afforded the corresponding lactones in good-to-high yields under mild conditions. This method was successfully employed in the synthesis of erythro-aleuritic acid lactone.
- Oohashi, Yoshiaki,Fukumoto, Kentarou,Mukaiyama, Teruaki
-
p. 1508 - 1519
(2007/10/03)
-
- Efficient method for the lactonization of ω-hydroxycarboxylic acids with di-2-thienyl carbonate by the promotion of catalytic amounts of DMAP and Hf(OTf)4
-
An efficient method for the synthesis of macrolides from ω-hydroxycarboxylic acids is established by using an equimolar amount of di-2-thienyl carbonate (2-DTC) and catalytic amounts of 4-(dimethylamino) pyridine (DMAP) and group 4 metal triflates such as hafnium(IV) trifluoromethanesulfonate (Hf(OTf)4). Copyright
- Oohashi, Yoshiaki,Fukumoto, Kentarou,Mukaiyama, Teruaki
-
p. 710 - 711
(2007/10/03)
-
- An effective method for the synthesis of carboxylic esters and lactones using substituted benzoic anhydrides with Lewis acid catalysts
-
An efficient mixed-anhydride method for the synthesis of carboxylic esters and lactones using benzoic anhydride having electron withdrawing substituent(s) is developed by the promotion of Lewis acid catalysts. In the presence of a catalytic amount of TiCl2(ClO4)2, various carboxylic esters are prepared in high yields through the formation of the corresponding mixed-anhydrides from 3,5-bis(trifluoromethyl)benzoic anhydride and carboxylic acids. The combined catalyst consisting of TiCl 2(ClO4)2 together with chlorotrimethylsilane functions as an effective catalyst for the synthesis of carboxylic esters from free carboxylic acids and alcohols with 4-(trifluoromethyl)benzoic anhydride. Various macrolactones are prepared from the free ω-hydroxycarboxylic acids by the combined use of 4-(trifluoromethyl)benzoic anhydride and titanium(IV) catalysts together with chlorotrimethylsilane under mild reaction conditions. The lactonization of trimethylsilyl ω-(trimethylsiloxy) carboxylates using 4-(trifluoromethyl)benzoic anhydride is also promoted at room temperature in the presence of a catalytic amount of TiCl 2(ClO4)2. An 8-membered ring lactone, a synthetic intermediate of cephalosporolide D, is successfully synthesized according to this mixed-anhydride method using 4-(trifluoromethyl)benzoic anhydride by the promotion of a catalytic amount of Hf(OTf)4.
- Shiina, Isamu
-
p. 1587 - 1599
(2007/10/03)
-
- A new method for the polymer-supported synthesis of cyclic oligoesters for potential applications in macrocyclic lactone synthesis and combinatorial chemistry
-
Attachment of ω-hydroxyalkanecarboxylic acids to Merrifield beads followed by treatment with a catalytic amount of di-n-butyltin oxide in chlorobenzene at 133 °C for 4-18 h brought about the formation of the corresponding cyclic oligomers (COs) as the mai
- Ruddick, Clare L.,Hodge, Philip,Cook, Anthony,McRiner, Andrew J.
-
p. 629 - 637
(2007/10/03)
-
- Scandium trifluoromethanesulfonate as an extremely active Lewis acid catalyst in acylation of alcohols with acid anhydrides and mixed anhydrides
-
Scandium trifluoromethanesulfonate (triflate), which is commercially available, is a practical and useful Lewis acid catalyst for acylation of alcohols with acid anhydrides or the esterification of alcohols by carboxylic acids in the presence of p-nitrobenzoic anhydrides. The remarkably high catalytic activity of scandium triflate can be used for assisting the acylation by acid anhydrides of not only primary alcohols but also sterically-hindered secondary or tertiary alcohols. The method presented is especially effective for selective macrolactonization of ω-hydroxy carboxylic acids.
- Ishihara, Kazuaki,Kubota, Manabu,Kurihara, Hideki,Yamamoto, Hisashi
-
p. 4560 - 4567
(2007/10/03)
-
- A Novel Method for the Preparation of Macrolides from ω-Hydroxycarboxylic Acids
-
An efficient method for the synthesis of macrolides directly from ω-hydroxycarboxylic acids is established by using 4-(trifluoromethyl)benzoic anhydride and a catalytic amount of active titanium(IV) salts together with chlorotrimethylsilane under mild conditions.
- Shiina, Isamu,Mukaiyama, Teruaki
-
p. 677 - 680
(2007/10/02)
-
- Tin(IV)-catalyzed lactonization of ω-hydroxy trifluoroethyl esters
-
1,1,1-Trifluoroethyl esters of ω-hydroxycarboxylic acids were prepared and their conversion to macrocyclic lactones, including ricinelaidic lactone, was studied in the presence of catalytic quantities of tin(IV) reagents; a mechanism involving exchange of alkoxytrialkyltin species is proposed.
- White,Green,Fleming
-
p. 3515 - 3518
(2007/10/02)
-
- MACROCYCLIC LACTONES VIA BIOCATALYSIS IN NON-AQUEOUS MEDIA
-
The enantiospecificity of lipase-catalyzed lactonization of chiral (w-1)-hydroxy acids to form diolides in non-aqueous medium was investigated.
- Zhi-wei, Guo,Ngooi, T. K.,Scilimati, A.,Fuelling, Gerd,Sih, Charles J.
-
p. 5583 - 5586
(2007/10/02)
-
- LIPASE CATALYZED SYNTHESIS OF MACROCYCLIC LACTONES IN ORGANIC SOLVENTS
-
A new method for the preparation of macrocyclic lactones from ω-hydroxyacid methyl esters is described.The approach utilizes intramolecular transesterification catalyzed by lipase in organic solvents.The procedure is also applicable to the synthesis of asymmetric lactones.
- Makita, Atushi,Nihira, Takuya,Yamada, Yasuhiro
-
p. 805 - 808
(2007/10/02)
-
- Preparation of Macrocyclic Lactones by Ring Closure of Cesium Carboxylates
-
A series of ω-halo fatty acids, the longest being 16-iodohexadecanoic acid, was prepared by oxidation of the corresponding ketones with m-chloroperbenzoic acid in boiling chloroform, followed by ring opening usually with hydrogen iodide in acetic acid at 100 deg C.Solutions of these acids in dimethylformamide (DMF) at concentrations of 5E-3 - 5E-2 M were treated with an equivalent amount of dry Cs2CO3.The solutions were stirred at 40 deg C overnight.Workup of the reaction mixture produced a mixture of (macro)cyclic lactone (macrolide) and its dimer (dilide).For the case of 16-iodohexanoic acid the lactone was isolated in 85percent yield.Yields for other large ring macrolides were also excellent.It was demonstrated that substitution by carboxylate on a secondary halide also goes well to afford the corresponding macrolide with no detectable amount of elimination.The effects of ring size, concentration, and solvent on the ring closure of the cesium carboxylates formed in situ were investigated.DMF is the best solvent of those investigated for the ring closure.Cesium carboxylates also undergo more readily ring closure and in far better yield than the carboxylates of lithium, sodium, potassium, rubidium, silver, thallium, magnesium, strontium, or barium.The S-lactone of ricinelaidic acid was prepared optically pure in 80percent yield from optically pure mesylate of R-ricinelaidic acid, which was treated with cesium carbonate in dry DMF.This demonstrates that the ring closure proceeds with the anticipated SN2 inversion at the hydroxyl-bearing carbon atom.With the same approach optically pure S-zearalenone was protected and subjected to ring opening, and the hydroxyl group was activated as mesylate.Some racemization was found to occur in the ring-opening step.On treatment of this material with dry cesium carbonate in DMF, the desired ring closure took place in 80percent yield to provide an excess of the protected R enantiomer of zearalenone.On the basis of these results, some speculations are made concerning the action of cesium in promoting ring closure to macrocyclic lactones.
- Kruizinga, Wim H.,Kellogg, Richard M.
-
p. 5183 - 5189
(2007/10/02)
-