Lactone opening butyrolactone

Five-membered lactones (y-butyrolactones) fused to carbohydrates have proven to be convenient synthons towards branched-chain sugars through opening of the lactone unit. Velaskes et al. [208] described the synthesis of y-butyrolactones... 

The five-membered unsubstituted lactone y-butyrolactone (y-BL) may not polymerize when using a conventional chemical catalyst. However, it was reported that only an oligomer was produced by the ring-opening polymerization of y-BL using PPL or lipase from Pseudomonas sp. [11,36]. 

The elucidation of the mechanism of ring-opening copolymerization of cyclic urea and carbonates offered opportunihes to study the general applicability of this mechanism to the copolymerizahon of tetramethylene urea with other monomers. The five-membered lactone, y-butyrolactone, is a readily available and cheap monomer, which may barely be homopolymerized (see Chapter 11). The copolymerization of tetramethylene urea with y-butyrolactone in the presence of dibutyl-magnesium as catalyst in the melt at 100 °C resulted in an alternating poly(amide urethane) (M = 12 600gmoT M = 21000gmoT = 1.67) [64]. 

Rea.ctlons, Butyrolactone undergoes the reactions typical of y-lactones. Particularly characteristic are ring openings and reactions in which ring oxygen is replaced by another heteroatom. There is also marked reactivity of the hydrogen atoms alpha to the carbonyl group. 

Other methods include ring opening of parasorbic acid [108-54-3] (5-lactone of 5-hydroxy-2-hexenoic acid) in hydrochloric acid or in alkaline solutions (43,44), the ring opening of y-vinyl- y-butyrolactone in various catalysts (45,46), or isomerization of 2,5-hexadienoic acid esters (47,48). Other methods are described in thehterature (6,49,50). 

Free radical polymerization of cyclic ketene acetals has been used for the synthesis of polyfy-butyrolactone), which cannot be prepared by the usual lactone route due to the stability of the five-membered ring. The polymerization of 2-methylene-l,3-dioxalane at high temperatures (above 120 °C) gave a high molecular mass polyester [59,79]. Only 50% of the rings opened when the polymerization was carried out at 60 °C, and this led to the formation of a random copolymer. The presence of methyl substituents at the 4- or 5-position facilitated the reaction. The free radical initiators generally used in such polymerizations are ferf-butyl hydroperoxide, ferf-butyl peroxide, or cumene hydroperoxide. The various steps involved are described in Scheme 5 [59]. 

When methyl 2-(trimethylsiloxy)cyclopropanecarboxylates 17 were treated with potassium borohydride in methanol, y-butyrolactones 18 were obtained in high yield. The first step in this reaction is thought to be desilylation and ring opening by methoxide ion generated in situ from methanol and borohydride. Subsequent reduction of the ketone leads to the secondary alcohol that reacts intramolecularly with the ester group to give the lactone. 

Thus, the ring opening of /3-proplolactone takes place almost exclusively at the alkyl-oxygen bond to form a porphlnatoalumlnum carboxylate (Equation 2a) (7). The same conclusion was obtained for the oligomerization of 0-proplolactone and butyrolactone as a result of 1H-NMR and 13C-NMR spectroscopy. As expected, the equimolar reaction product of TPPAlEt (1e) and carboxylic acid (cf. Equation 3) Is a good Initiator for the polymerization of lactone and yields a polymer with narrow molecular weight distribution. 

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