Ring expanded 5-lactone

The Baeyer-Villiger transformation of several protected derivatives having a free ketone group has been effected by m-chloroperoxybenzoic acid. Thus, 1,6-anhydro-3,4-0-isopropylidene-/f-D-/yxn-hexopyranos-2-ulose (28) was converted into the cyclic, orthoacid anhydride 29.67 As an additional example, the Baeyer-Villiger oxidation of Ferrier carbocyclization products derived from D-glucose afforded 5-deoxyhexofuranosiduronic acids, via the ring-expanded lactonic intermediates68 (Scheme 12). 

High yields are obtained also in the oxidation of cyclic ketones to the ring-expanded lactones. ... 

Scheme 9. Synthesis of ring-expanded lactones and lactams...

Pummerer rearrangement processes have been described in several papers. -Typically, RS(0)(CHg)4SR-> RSCH=CH(CHa)2SR on treatment with AcjO, and the formation of the ring-expanded lactone via 2-hydroxy-2-methylsulphinylmethyltetrahydrofuran, illustrate the possibilities of these processes in synthesis. A silicon-Pummerer rearrangement, MeaSi-CH,jS(0)Ph-> CH8=S(OSiMea)Ph McsSiOCHaSPh, effected at 60 °C, has been studied further some seven years after the process was discovered substantial amounts of vinyl sulphides are also formed. 

Reactions of carbocyclic P-keto esters, sulfonium ylides and enamines with activated alkynes such as DMAD are known to result in formation of (n + 2) ring expanded products. In a study of the analogous reactions of carbocyclic p-keto phosphonates, it was found that in the cases of the simple cyclic P-keto phosphonates 1, ring expansion occurred to give 2 in reasonable yield. Extension of the method to the tetralone 3, however, led to formation of two products, the "expected" (n + 2) ring expansion product analogous to 2 (37%), and the lactone 4 (29%). 

Baeyer-Villiger oxidation of a cyclic ketone normally gives a ring-expanded lactone22 so lactone 11 is the expected Baeyer-Villiger product of 7, not formates 8 and 9. This unexpected observation may be due to the fact that 7... 

After conjugate addition of the hydroperoxide anion to the chelated a,p-unsaturated lactone, the resulting enolate counterattacks the proximal [3-hydroperoxide group to form an epoxide. The latter then ring-expands to create another enolate, which captures a proton from water. The product hemiacetal finally undergoes ring-opening and saponification to produce 9 (Scheme 6.5). 

Photochemical decomposition of malonic acid by irradiation in solution has been reported. Some of the radical species produced by this treatment are identical to those formed by the Ce decomposition of malonic acid in the Belousov-Zhabotinsky reaction. The (2 + 2)-cycloadducts (172) can be readily prepared by irradiation of mixtures of the corresponding enone and alkene, and these adducts can conveniently be converted into the hydroperoxide (173) by irradiation at 366 nm in the presence of air and acridine in toluene.The decarboxylation occurs by a free radical pathway and treatment of the hydroperoxide with dimethyl sulfide brings about formation of the ring-expanded ketones or lactones (174),... 

The linear triquinane skeleton is easily accessible from methyl 8-oxotricyclo-[5.4.0.0] undecan-l-carboxylate 67 [64]. Photoreduction of 67 affords ring-expanded intermediate 67" which cyclizes to the linearly fused triquinane 68 (Scheme 29, eq 1). An extension of this reaction to the heterocyclic angular tricyclic compound 70 has also been achieved starting from keto lactone 69 (Scheme 29, eq 2) [75]. 

Azithromycin, called an azalide, has been formed by semisynthetic conversion of erythromycin to a ring-expanded analogue in which an N-methyl group has been inserted between carbons 9 and 10, and the carbonyl moiety thus is absent (Fig. 38.28). Azithromycin has a 15-membered lactone ring. 

Ninhydrin (858) reacts with p-cresol in the presence of zinc chloride to yield the eight-membered lactone (859). Generation of the carbene (860) from the corresponding diazopyrazole in the presence of benzene derivatives PhR (R = MeO, Me, Cl, CN, or NO2) results in mixtures of isomeric substitution products (861) and ring-expanded pyrazolo-azocines (862) electron-withdrawing substituents enhance the formation of the latter cf. p. 158). The oxadiazoloben-zodiazocinone (864) is formed by the action of phosgene on the iV-oxide (863). ... 

The Schmidt reaction of a simple cyclic ketone yields lactams with the ring expanded, while the intramolecular Schmidt reaction of cyclic ketone with an azido group at the side chain leads to the formation of bicyclic lactams with nitrogen at the position of fusion. It is interesting that the reaction between a cyclic ketone and 2-azido ethanol can form either a lactam or a lactone by means of the treatment with a different base, in which the lactam is formed when the reaction system is treated with KOH, whereas lactone is generated when NaHCOs is used as the base. Especially, the reaction between 4-ferf-butylcyclohexanone and 3-azido-2-methyl-2-phenylpropanol gives lactam in 19 1 stereoselectivity. ... 

Sol 2. (i) The conversion of P-dimethyl substituted a-lactone (I) to the ring expanded p-lactone (II) proceeds through a dyotropic transition state. 

More highly substituted aromatics have also been studied in the course of natural product synthesis. For example, rhodium(II) mandelate-catalyzed cyclization of diazoketone 41 produces the ring expanded product 42, which on hydrogenations furnishes the tricyclic lactone 43. ... 

Silver-ion assisted hydrolysis of the 4-homoadamantane-dichlorocarbene adduct 112) affords 4-homoadamantyl carboxylic acid, the ring-expanded product (773) and the unusual lactone (774), the product yields and individual ratios being rather dependent on the reaction conditions. The lactone (774) is probably a product of rearrangement of a homoadamantyl cation produced by protonation of an acid or aldehyde of structure (775 R = CHO or COjH). 

Gravel et al. [71] reported an interesting methodology for y-lactone formation through ring-expanding reaction of oxetane-2-carbaldehyde 103 (Scheme 46). N-Heterocyclic carbene derived from an imidazolinium salt 105 was found as the most potent catalyst for this reaction. This reaction is also applicable for the synthesis of 8-pentanolides. 

Terminal-functionalized polymers such as macromonomers and telechelics are very important as prepolymer for construction of functional materials. Single-step functionalization of polymer terminal was achieved via lipase catalysis. Alcohols could initiate the ring-opening polymerizahon of lactones by lipase catalyst. The lipase CA-catalyzed polymerizahon of DDL in the presence of 2-hydroxyethyl methacrylate gave the methacryl-type polyester macromonomer, in which 2-hydroxyethyl methacrylate acted as initiator to introduce the methacryloyl group quanhtatively at the polymer terminal ( inihator method ).This methodology was expanded to the synthesis of oo-alkenyl- and alkynyl-type macromonomers by using 5-hexen-l-ol and 5-hexyn-l-ol as initiator, respechvely. 

The lactone concept is not restricted to the simple model biaryl synthesis presented here. It has been successfully expanded to a broad series of structurally diverse biaryl substrates (e.g., lactones with additional stereocenters and functional groups, configurationally stable lactones, seven-membered lactones, and again configurationally unstable biaryl hydroxy aldehydes ), to different activation modes in the ring-opening step (e.g., use of metallated nucleophiles, carbonyl activation by Lewis acids, (Ti -complexation, etc.), and for various strategies of stereoselection (e.g., external vs. internal asymmetric induction). ... 

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