Lactones, from acrylate esters

Optimum yields of (3-vinyl-y-butyrolactols from the Pd(II) promoted reaction of vinyl triflates with Z-but-2-en-l,4-diol (Scheme 6.33) are attained when tetra-n-butylammonium chloride is added (47]. The lactol is conveniently oxidized to the lactone with celite-supported silver carbonate. The corresponding arylbutyrolactols are obtained in high yield (70-80%) from an analogous reaction of iodoarenes with the enediol. The yields of 2-alkenyl-2,5-dihydrofurans, resulting from the Pd(0) catalysed reaction of cyclic alkynylcarbonates with acrylic esters via tandem C-C and C-0 bond forming reactions, are enhanced by the presence of tetra-n-butyl-ammonium fluoride (e.g. Scheme 6.33) (48]. 

Vobtusine Lactone (270) and Desoxyvobtusine Lactone (271).— These bases differ from the previously described vobtusine relatives in that instead of a five-ring ether function in part B they contain a y-lactone. Both alkaloids exhibit u.v. spectra identical to that of vobtusine (255). In the i.r. spectrum the )8-anilino-acrylic-ester bands as well as a band at 1795 cm S typical of a y-lactone are apparent. 

C-Alkylation of 1 with ethyl 2-iodopropionate gave 86 whose lactonization afforded 3,6,6-trimethylbenzofuran-2-one 87 (84CPB2249). While 1 with ethyl a-bromoacrylate in the presence of potassium carbonate in DMSO gave benzofuran 88. The reaction is due to a Michael addition of the carbanion obtained from 1 to the activated double bond of the acrylate ester to give an intermediate C-alkylated adduct that spontaneously cyclized to 88 (86ZOR2262) (Scheme 15). 

Class 2 RCM reactions, involving the use of homoallyhc acrylate esters to form unsaturated lactones, have also found synthetic utility in the context of THP-containing natural products. These acrylate substrates are rapidly accessed from the straightforward esterification of a homoaUylic alcohol. While the second class does not formally yield a THP, the lactone affords the appropriate handles for a reductive acetylation/alkylation protocol, which is a powerful method for THP functionalization (Sect. 6.2). 

Since the exocyclic sulfur is more reactive in the ambident anion than in A-4-thiazoIine-2-thione. greater nucleophilic reactivity is to be expected. Thus a large variety of thioethers were prepared in good yields starting from alkylhalides (e.g.. Scheme 38 (54, 91, 111, 166-179). lactones (54, 160), aryl halides (54, 152. 180, 181), acyl chlorides (54. 149, 182-184). halothiazoles (54, 185-190), a-haloesters (149. 152. 177. 191-194), cyanuric chloride (151). fV.N-dimethylthiocarbamoyl chloride (151, 152. 195. 196), /3-chloroethyl ester of acrylic acid (197), (3-dimethylaminoethyl chloride (152). l,4-dichloro-2-butyne (152), 1,4-dichloro-2-butene (152), and 2-chloro-propionitrile (152). A general... 

This polymeric lipid can first be polymerized by free radical initiator in organic solutions before making the vesicles. The proton NMR spectrum of the polymerized lipid shows that vinyl protons of the cyclic acrylate between 85.00 ppm and 86.00 ppm disappeared from the spectrum, compared with that of monomeric lipid. Also in the IR spectrum (Figure 6) the absorption peak at 1670 cm"1 for the cyclic acrylate carbon carbon double bond disappeared as the result of polymerization. The carbonyl absorptions of the esters at 1740 cm 1 and the lactone at 1805 cm"1 still remain in the spectrum. 

Fig (19) Octalin ketal (163) is converted to kete dithioacetal (164) by the cleavage of ketal function and condensation with carbon disulfide and methyl iodide. Subjection of (164) to the action of dimethylsulfonium niethylide and acid hydrolysis leads to the formation of unsaturated lactone (165).lts furan silyl ether derivative is caused to undergo Diets-Atder reaction with methyl acrylate to obtain salicyctic ester (166) which is converted by standard organic reactions toabietane ether (167). It is converted to aiiylic alcohol (168) by epoxidation and elimination. Alcohol (169) obtained from (168) yields orthoamide which undergoes transformation to amide (170). Its conversion to the previously reported intermediate has been achieved by epoxidation, elimination and hydrolysis. 

The ability to accept electrons from donors is particularly pronounced in acrylic acid derivatives [85] its alkyl esters [78, 87, 88], acrylonitrile [88], acrylamide, hydroxylacrylates [85], and further in styrenes substituted with an electronegative atom or group m-nitrostyrene, 2,6-dichlorostyrene [86], / -nitrostyrene [89] bicyclobutane-1-carbonitrile [89] lactones /J-propio-Iactone [85], sulfolactone vinyl ketones [87] unsaturated dicarboxylic acids and their derivatives diethyl fumarate, fumaronitrile [90], ROOC—N— N—COOR [86], cyclic anhydrides of diacids [91 ], particularly maleic anhydride [78, 92] ethylenes substituted with electronegative groups [93, 95]... 

Here, we will discuss some fundamental aspects of the selectivity of Novozym 435 —Candida antarctica Lipase B immobilised on an acrylic resin— for (o-substituted lactones. This selectivity determines the polymerisability of a (D-substituted lactone employing Novozym 435 as the catalyst. We will first address the influence of the conformation of the ester bond in the lactone cisoid or transoid) on the selectivity of the ring-opening of a selection of lactones with ring sizes vaiying from a 4- to 13-membered ring. Then, we will address the influence of the size of the substituents at the co-position on the selectivity and... 

This new method for the construction of a-hydroxy-y-lactones is quite general for a variety of alcohols and a,P-unsaturated esters (Figure 6.9). The preparation of a-hydroxy-y-spirolactones from cyclic alcohols is especially notable, because these spirolactones have been very difficult to synthesize until now. The reaction can be explained by Scheme 6.18 (i) in situ generation of an a-hydroxy carbon radical from an alcohol assisted by NHPI/Co(II)/02, (ii) the addition of the radical to methyl acrylate, (iii) trapping of the adduct radical by O2, and (iv) intramolecular cydization to give a-hydroxy-y-butyrolactone. Considering the low-cost material, reaction efficiency, and reaction simplicity, this method provides an innovative approach to a-hydroxy-y-lactones which has considerable industrial potential. 

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