Lactone synthesis reactions

Jacobson-Hugershofi synthesis benzothiazoles, 5, 135 Japp-KJingemann reaction JV-arylhydrazones from, 4, 337 1,2,4-triazole synthesis by, 5, 768 Jasmine lactone synthesis, 3, 847 Jasminine occurrence, 2, 626 y-Jasmolactone synthesis, 4, 674 cis-Jasmone synthesis, 1, 422, 427 Jatropham synthesis, 1, 426 Josephson junctions, 1, 359 Juliprospine... 

Lactams 618 <5-Lactols 627 Lactones 617 reactions of 636 synthesis of 632, 737, 815 a,fl-unsaturated - see a,/J-Unsaturated lactones... 

The focus of this review is to discuss the role of Cinchona alkaloids as Brpnsted bases in organocatalytic asymmetric reactions. Cinchona alkaloids are Lewis basic when the quinuclidine nitrogen initiates a nucleophilic attack to the substrate in asymmetric reactions such as the Baylis-Hillman (Fig. 3), P-lactone synthesis, asymmetric a-halogenation, alkylations, carbocyanation of ketones, and Diels-Alder reactions 30-39] (Fig. 4). 

In 1994, Quayle et al. reported the application of this cyclic Fischer-carbene synthesis from 3-butynols to spirolactone synthesis, although the process was stepwise and a stoichiometric amount of the complex was employed [17]. The key transformation was the chromium or tungsten carbene complex formation followed by the CAN oxidation of the complex to give y-lactone. The reaction was further applied to the synthesis of andirolactone and muricatacin, the former being shown in Scheme 5.14. 

The first surface-initiated enzymatic polymerization reported was the synthesis of amylose brushes on planar and spherical surfaces [145]. For this, silica or silicone surfaces were modified with self-assembled monolayers of (3 amino-propyl)trimethoxysilane or chlorodimethylsilane, respectively. To these functionalities, oligosaccharides were added via (a) reductive amidation of the oligosaccharides to surface-bound amines, (b) conversion of the oiigosaccharide to the according aldonic acid lactone and reaction with surface bound amines, and (c) incorporation... 

The most recent method for /3-lactone synthesis involves a very novel approach. Phenyl-ethynolate anion (which may be in equilibrium with phenylketene anion) can be generated by the reaction of n-butyllithium or f-butyllithium in THF at -78 °C. This highly nucleophilic species reacts with cyclohexanone to give the spiro-/3-lactone (54), probably through intermediacy of the lithium alkoxide of the /8-hydroxyketene (53). The /3-lactone (54) was isolated in about 50% yield (79LA219,82JA321). 

Adrenolactone (3). A new synthesis of the lactone involves reaction of the tetrahydropyranyl derivative of 3/ -hydroxy-17-ketoandrostene (2) with the dilithio derivative of 1. 

The Fischer cyclization of phenylhydrazones of structure (18) gives rise to the carbinolamine-lactones (19). Reaction with methylamine, followed by reduction, then affords a short synthesis of esermethole (20a) and eserethole (20b) (Scheme... 

The nucleophile-catalyzed aldol lactonization (NCAL) reaction of carboxyl-derived zwitterions and unactivated aldehydes has been applied to the catalytic asymmetric synthesis of bicyclic /3-lactones (Equation 31)... 

Andreana et al. [25] have recently invoked RCM to prepare /J,y-unsaturated <5-lactones (Scheme 3). Exposure of dienes of general type 13 to either 2 or 4 (which could be used at lower loadings) readily furnished lactones 14. For other examples of a,/ -unsaturated <5- and y-lactone synthesis by RCM see Ref. [26]. Variation of the configuration at the chiral carbons and the ligand for the asymmetric dihydroxylation reaction allows access to an array of biologically important dideoxy-sugar derivatives. 

Both ketones and aldehydes, as well as acylsilanes can be employed as carbonyl substrates in the new p-lactone synthesis (Table). Reactions involving ketones are most conveniently carried out by adding the neat carbonyl compound to the thiol ester enolate solution. Under these conditions aliphatic aldehydes react to form substantial quantities of 2 1 adducts however, formation of these side products can be suppressed simply by slowly adding the aldehyde component as a precooled (-78°C) solution to the reaction mixture. Wide variation is also possible in the thiol ester component, although a few limitations of the method have been noted. For example, a,p-unsaturated ketones such as methyl vinyl ketone and cyclohexenone fail to yield p-lactones, and attempts to generate p-lactones with severe steric crowding have also met with limited success.3... 

One of the earliest examples of the synthetic promise of radical reactions for preparing polycyclic products was provided by Corey s y-lactone synthesis. This approach was actually based on a well-known reaction of a-carbonyl radicals, generated by manganese(iii) oxidation of carboxylic acids, with unsaturated substrates. The mechanism of the basic steps shown for the preparation of lactone 418 (Scheme 2.140) involves initial addition of the a-carbonyl radical 419 to the double bond of styrene, followed by oxidation of the radical intermediate 419a to carbocation 419b, and subsequent intramolecular reaction with the carboxyl nucleophile to yield the lactone product. 

Unsaturated lactones lacking substitution at C-4 are the simi est ones available via this general type of cycloaddition. Several syntheses of these lactones are of practical value, including two Pd-based meth-ods. However, the considerable utility of metal carbonyl anions in lactone synthesis is illustrated by a rhodium carbonyl anion catalyst system which gives very high yields upon reaction with a variety of internal alkynes under weakly basic aqueous conditions, essentially water-gas shift conditions. These conditions were established to maximize chemoselectivity with respect to other possible alkyne carbonylation products. Regioselectivity is modest in this process, but was not examined systematic ly (equation 13). ... 

An aldol reaction with chiral /3-benzyloxy aldehyde provides a method for the stereodivergent synthesis of both syn and anti diastereomers [97] with high diastereo-selectivity dictated primarily by the chirality of the BINOL-Ti catalyst (1) rather than the /1-benzyloxy aldehyde (Sch. 37) [98]. The aldol products can be used as useful key intermediates for /1-lactone synthesis [99]. 

A preliminary report has appeared from Wolinsky s laboratory concerning the cyclization of methyl ( )-epoxycitronellate (80) by the action of sodium hydride in dimethylformamide. This leads to the two lactones [(81) and (82)] and three unsaturated acids [(83)—(85)], the acids being formed via the action of sodium methoxide on the lactones. This reaction has led to a synthesis of dihydronepetalactone [the cis,cis,trans-S-meihy isomer of (74) and (75)]. ... 

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