Ring Opening of Cyclic Anhydrides

Sabitha and coworkers have introduced a rapid and high yielding procedure for the preparation of half-esters (160) from cyclic anhydrides using the requisite alcohol and Bp3 OEt2 (Equation 95) [97]. Compared to the other Lewis acids attempted, the reaction with Bp3 OEt2 is spontaneous and clean, and requires only a simple work-up. 

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Enantioselective alcoholysis of racemic, prochiral, or meso cyclic anhydrides can be catalyzed by hydrolases, yielding the corresponding monoesters (Eigure 6.25). In most cases, the enantioselectivity was moderate ]75-77]. Organometallic catalysts or organocatalysts such as cinchona alkaloids are often more efficient than enzymes for the stereoselective ring opening of cyclic anhydrides. 

SCHEME 10. Asymmetric ring opening of cyclic anhydrides. 

Ring-opening of cyclic anhydride 4 by aminolysis and subsequent formation of the second amide function led to the diamides, 5b. Either the mero-isomer or the ( -symmetrical chiral derivative is thus available in a controlled way.19... 

SCHEME 15. Synthesis of C2-symmetric derivatives fixed in the 1,3-alternate conformation by ring opening of cyclic anhydrides... 

K. Yamamoto, T. Nishioka, J. Oda, Y. Yamamoto, Asymmetric Ring Opening of Cyclic Acid Anhydrides with Lipase in Organic Solvents , Tetrahedron Lett. 1988, 29, 1717-1720. 

V. Selective Ring-opening of Cyclic Acetals with Carboxylic Acid-Trifluoroacetic Anhydride Mixtures... 

C. Bolm, I. Schiffers, C.L Dinter, A. Gerlach, Practical and highly enantioselective ring opening of cyclic meso-anhydrides mediated by cinchona alkaloids, J. Org. Chem. 65 (21) (2000) 6984-6991. 

Our final example is that of cyclic anhydrides, namely prochiral 3-sub-stituted glutaric anhydrides (7.101, R = Me, Et, or Pr). When incubated with lipase in an inert solvent in the presence of an alcohol (methanol, butan-l-ol, etc.), these compounds underwent nucleophilic ring opening with formation of a hemiester (7.102) of (/ -configuration (60-90% ee) [180]. This product enantioselectivity and, of course, the lack of reactivity in the absence of lipase show the enzymatic nature of the reaction. 

Conventional ring-opening polymerization of cyclic anhydrides, carbonates, lactones, and lactides require extremely pure monomers and anhydrous conditions as well as metallic catalysts, which must be completely removed before use, particularly for medical applications. To avoid these difficult restrictions, an enzymatic polymerization may be one of the more feasible methods to obtain the polyesters. This method was first reported by two independent groups (Kobayashi [152] and Gutman [153]) who showed that lipases, enzymes capable of catalyzing the hydrolysis of fatty acid esters, can polymerize various medium-sized lactones. 

Spivey, A. C. Andrews, B. I. Catalysis of the Asymmetric Desymmetrization of Cyclic Anhydrides by Nucleophilic Ring-Opening with Alcohols, Angew. Chem. Int. Ed. 2001, 40, 3131-3134. 

There has been considerable interest in the stereoselective ring opening of meso-cyclic anhydrides. The stereoselective alcoholysis of these anhydrides is particularly attractive as the resulting hemiesters are used as versatile intermediates in the construction of many bioactive compounds [1], Much effort has, therefore, been devoted to the development of efficient enzymatic and nonenzymatic catalytic systems for this reaction [2], Among the stereoselective catalysts developed to date,... 

Nucleophilic ring opening of the cyclic sulfinic-carboxylic anhydride (11) is found to occur exclusively by attack at C=0 <86KFZ843, 88IZV1633>. 

Radical addition of allyl alcohol to cyclododecanone and dehydrative cycli-sation gives a bicyclic dihydropyran. The ring-opening of the cyclic acetal of cyclododecanone with triisopropylaluminium and reclosure using trifluoro-methanesulfonyl anhydride provides an interesting alternative. The 15-hydroxy-pentadecanoic acid is then accessible by means of nitrosation, followed by Wolff-Kishner reduction. Apart from the reduction with hydrazine, catalytic, electrochemical and Clemmensen reduction are also well-established. 

Y. S. Gal, S. H. Jin, A self-doped ionic conjugated polymer poly(2-ethynyl-pyridinium-N-benzoylsulfonate) by the activated polymerization of 2-ethynylpyridine with ring-opening of 2-sulfobenzoic acid cyclic anhydride, Bulletin of the Korean Chemical Society 2004, 25, 777. 

Cyclic compounds capable of undergoing ring opening (alkylene oxides, lactones, lactams, anhydrides, etc.). 

Lipase-catalyzed synthesis of polyesters from cyclic anhydrides and oxi-ranes was reported. The polymerization took place by PPL catalyst and the molecular weight reached 1 x 10" under the selected reaction conditions. During the polymerizahon, the enzymatically formed acid group from the anhydride may open the oxirane ring to give a glycol, which is then reacted with the anhydride or acid by lipase catalysis, yielding the polyesters. 

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