Ethers, cyclic from lactones

Crivello and Lam have demonstrated the use of diaryliodonium salts as photoinitiators for polymerization of electron-rich olefins, cyclic ethers, cyclic sulfides, lactones and spiro orthoesters, but a vast majority of their published work concerns polymerization of substituted oxiranes, illustrating the potential of such systems in photocuring of epoxy resins. Such polymerizations can be quite fast in the most favorable example, a 93% yield of polymer of Mn 10,700 was obtained from 3-vinylcyclohexene oxide after only 90 seconds of irradiation at room temperature with 4,4 -di-tert-butyldiphenyliodonium hexafluoroantimonate as initiator (3). The substituted salts are often preferred to the simple unsubstituted diphenyliodonium compounds for reasons of solubility (2). The use of diaryliodonium salts in combination with various dyes allows one to initiate cationic polymerization with visible light (5). 

This very hindered secondary alcohol—located in a complex molecule—can be efficiently oxidized to the corresponding ketone in a biphasic system, using Ru04 generated from RuC13 and excess of NaI04. An additional oxidation of a cyclic ether to a lactone occurs under the reaction conditions. 

Instead of enol triflate, the enol phosphate 334, derived from lactone 333, is used for the coupling to afford the cyclic enol ether 335. No coupling of phenyl phosphate... 

Cyclic ethers from lactones. The ready addition of RLi to the C=S group of thionolactones (14, 9) has been used to prepare functionalized cyclic ethers from lactones of the same ring size. The first step involves Lawesson thionation of lactone... 

Using tetrafluoroboric acid, several unsaturated acids and nitriles were thus made reactive and were converted into acetoxy lactones [3]. Tosyloxy-, phosphoryloxy-and iodomethyl lactones as well as cyclic ethers resulting from analogous neighbouring group participation will be discussed in connection with other hypervalent iodine reagents. 

Cyclic diene ether 93 was prepared in high yield starting from lactone 163 through the corresponding enol triflate (Equation 8) C1995TL8263, 1997CL665>. 

The direct fluorination with elemental fluorine at — 78 "C of trimethylsilyl enol ethers derived from diketones results in the formation of the corresponding monofluoro diketones 11 in moderate yield. The trimethylsilyl ethers from cyclic diketones undergo smooth fluorination to give the enol forms, c.g. 12, and not the keto forms.Higher yields are generally observed for the analogous reactions of silyl derivatives of esters, carboxylic acids, malonates, dimethyl amides and lactones (Table 4). ... 

A large number of copolymers of cyclic ethers, cyclic sulphides and cyclic formals have been prepared. Many cyclic compounds that will not homopolymerize do copolymerize readily [7, 146,147]. Some cyclic compounds will copolymerize with lactones, cyclic anhydrides, or vinyl monomers. Very many commercially important materials have resulted from these copolymerizations. 

Intramolecular cyclization is a useful method for the preparation of lactones and cyclic ethers [34], The most common examples are iodolactonization and iodoetherification, the former using a carboxylic acid derivative as the nucleophile and the latter relying on a hydroxy group. Thus, butyrolactones are available from Y, -unsaturated carboxylic acid derivatives [1,35,36], while unsaturated alcohols lead to cyclic ethers [37-40], Lactones are also available from a wide variety of nucleophiles such as carbonates [41], orthoesters [42], or carbamates [43,44], which can all be used in place of a carboxylate anion [44,45],... 

Photolysis of the hypoiodite derived from N-acetyljervine (27) gave the dimeric compound (28) as the major product, together with small amounts of the iodides (29) and (30), the cyclic ether (31), and lactone (32). In a preliminary communication ( f. Vol. 5, p.263) the authors had misassigned the structures of several of... 

Via intermediates Reductive synthesis Cyclic ethers from lactones Isoflav-3-enes from coumarins... 

Disubst. cyclic ethers from lactones and two different Si-nucleophiles ... 

Trichlorosilaneldi-tert-butyl peroxidelirradiation Cyclic ethers from lactones... 

Apart from copoly(ester urethane)s, synthetic developments towards polymers containing polyester blocks have been dominated by two main themes, the first stemming from early work on block poly(ether ester)s and the second from interests in the ring-opening polymerization reactions of cyclic esters (lactones). 

Intramolecular Addition Formation of Cyclic Enol Ethers and Lactones from Pent-4-yn-1-ols and But-3-yn-1-ols... 

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