To lactone

Lactams are cyclic amides and are analogous to lactones which are cyclic esters Most lactams are known by their common names as the examples shown illustrate... 

Chiral Alcohols and Lactones. HLAT) has been widely used for stereoselective oxidations of a variety of prochiral diols to lactones on a preparative scale. In most cases pro-(3) hydroxyl is oxidized irrespective of the substituents. The method is apphcable among others to tit-1,2-bis(hydroxymethyl) derivatives of cyclopropane, cyclobutane, cyclohexane, and cyclohexene. Resulting y-lactones are isolated in 68—90% yields and of 100% (164,165). 

Figure 3.11 shows the relative reactivity as a function of ring size for two other intramolecular displacement reactions, namely, conversion of ethers from ca-bromoalkyl monoethers of 1,2-dihydroxyben-zene. 

There are related procedures involving A -haloamides which lead to lactones via iminolactone intermediates ... 

No systematic study of the minimal required amount of lead tetraacetate has been made. In cases where the product of the hypoiodite reaction is an iodo ether (20-hydroxy steroids) the reaction can be interrupted at the iodohydrin stage by reducing the amount of iodine to about 0.5 mole. For the oxidation of iodo ethers to lactones, chromium trioxide-sulfuric acid in acetone has been used. Silver chromate is often added to the reaction mixture but comparable yields are obtained without the addition of silver salt. 

Lactams aie cyclic fflnides and aie analogous to lactones, which aie cyclic esters. Most lactfflns aie known by their common nanes, as the examples shown illustrate. 

The reaction of peracids with ketones proceeds relatively slowly but allows for the conversion of ketones to esters in good yield. In particular, the conversion of cyclic ketones to lactones is synthetically useful because only a single product is to be expected. The reaction has been carried out with both percarboxylic acids and Caro s acid (formed by the combination of potassium persulfate with sulfuric acid). Examples of both procedures are given. 

Cleavage of the imidazolidine moiety by acidic hydrolysis led to chiral lactols 17, which can be further oxidized to lactones 19 or reduced to diols 1848. 

The difference in reactivity is perfectly revealed in Metz s total synthesis of the molluscicidal furanosesquiterpene lactones ricciocarpin A (50) and B (51) (Scheme 9) [32]. Attempts to convert acrylate 43 to lactone 44 using Grubbs5 catalyst A or Schrock s molybdenum catalyst B resulted in very low yields of the... 

In carboxylic acids with an aromatic group or a double bond the ii-systems can be oxidized to radical cations that react with the carboxyl group to lactones (Eqs. 7, 42) [142, 351]. 

Reduction of Cyclic Anhydrides to Lactones and Acid Derivatives to Alcohols... 

Ipomeamarone has been synthesised by a slight variant on this strategy in which the methyl group is added to lactone (47) and a Wittig reagent is used for synthon (42) ... 

Additions of silylated ketene acetals to lactones such as valerolactone in the presence of triphenylmethyl perchlorate in combination with either allyltrimethylsilane 82, trimethylsilyl cyanide 18, or triethylsilane 84b, to afford substituted cyclic ethers in high yields have already been discussed in Section 4.8. Aldehydes or ketones such as cyclohexanone condense in a modified Sakurai-cyclization with the silylated homoallylic alcohol 640 in the presence of TMSOTf 20, via 641, to give unsaturated cyclic spiro ethers 642 and HMDSO 7, whereas the 0,0-diethyllactone acetal 643 gives, with 640, the spiroacetal 644 and ethoxytrimethylsilane 13b [176-181]... 

The principles set forth above account reasonably well for the course of bifunctional condensations under ordinary conditions and for the relative difficulty of ring formation with units of less than five or more than seven members. They do not explain the formation of cyclic monomers from five-atom units to the total exclusion of linear polymers. Thus 7-hydroxy acids condense exclusively to lactones such as I, 7-amino acids give the lactams II, succinic acid yields the cyclic anhydride III, and ethylene carbonate and ethylene formal occur only in the cyclic forms IV and V. 

Other nucleophilic functional groups can participate in iodocyclization. Amides usually react at oxygen, generating imino lactones that are hydrolyzed to lactones.88... 

The sulfonyl substituent can be removed by reduction after the ring closure (see Section 5.6.2). Other appropriate reactants are a-phenylthio nitriles, which can be hydrolyzed to lactones.124... 

Application of the carbonylation reaction to halides with appropriately placed hydroxy groups leads to lactone formation. In this case the acylpalladium intermediate is trapped intramolecularly. 

The most versatile route to lactone color formers is based on the elegant synthesis of Malachite Green lactone described by Haller and Guyot in 1899.24 Scheme 3 illustrates the application of this route for the preparation of CVL. 

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