1,3-Dioxolane, ring-opening reaction

The 1,2,4-oxadiazole dioxolanes 144 react with hydroxylamine and hydrazines to form the 5-pyrazole- and isoxazole-substituted 1,2,4-oxadiazoles 146 via the dioxolane ring-opened intermediates 145 (Scheme 17). Reaction of compounds 144 with amidine or guanidine salts allows access to pyrimidine substituted analogues 147, via intermediate 145 (X = C(NH)R1), albeit in lower yield <1996JHC1943, 1998JHC161>. 

Further studies of 1,3-dioxolan ring-opening by phosphorus pentachloride (81) have appeared, and include a description of new quenching conditions for the reaction of 2-methyl-l,3-dioxolan (100). With2-methyl-4-chloromethyl-1,3-dioxolan (101), the second stage of the reaction with (81) is slow, and the... 

When benzoin derivatives are irradiated in the presence of arene diazonium salts or aryl iodonium salts cationic species are formed. These species initiate ring-opening reactions of glycidyl ether in the presence of ketones or aldehydes. The method, however, also forms dioxolane and formation of the dioxolane predominates over homopolymerization. ... 

TABLE 1. Copoly merization Scoping Reactions Using the Radical Ring-Opening Polymerization Monomer, 5-Methylene-2-phenyl-l,3-dioxolan-4-one, with Methyl Methacrylate... 

The electron transfer reaction of gem-diarylmethylenecyclopropanes (60) with singlet sensitizers results in the exchange of the exo-methylene and the secondary cyclopropane carbons [241], The chloranil photo-sensitized reaction generates two unusual cycloaddition products (61, 62) [242], whereas the tetracyanoethylene sensitized oxygenation produces the respective dioxolanes [238]. These reactions are compatible with a ring-opened radical cation, and CIDNP experiments have... 

It seems that the alkylene carbonate polymerisation proceeds via monomer decarboxylation in the first reaction step. The decarboxylation most probably involves metal carbonate species owing to ring opening of the 1,3-dioxolan-2-one via Cp—O bond cleavage [146,147]. A possible reaction scheme in the presence of zinc-based coordination catalysts is presented by scheme (14), in which, for the sake of clarity, participation of the adjacent zinc atom as the nucleophilic attack carrier is omitted ... 

In any event, no such phenomenon can explain the unretarded hydrolysis of 1,3-dioxolanes. The reaction is the exact analogue of the ring-opening of oxazolidines, and so the leaving group cannot become antiperiplanar to an sp3-type lone pair orbital on oxygen. In a detailed study, Fife and Jao (1965)... 

This reaction is thermodynamically controlled, because the polymer containing 1,3-dioxolane rings converts itself to a polyether when allowed to stand at room temperature for several days or heated at 80 °C for a few hours in the presence of an acid catalyst. Similar double ring-opening polymerizations were observed for 2,6,7-trioxabicyclo[2.2.2]octane and its derivatives [86, 87] and for spiro orthoesters and spiro orthocarbonates as well (see Sects. 6 and 7). 

Phenyselenyl chloride reacts with 2-alkyl-l,3-dioxolanes having at least one a-hydrogen atom to give a-phenylseleno products accompanied by considerable amounts of disubstituted products. It is probable that this reaction proceeds as shown in Scheme 14, with acid catalyzed ring opening to an enol followed by attack of the electrophilic selenium reagent (79S982). 

The action of strong base on 1,3-dioxolanes derived from /S,y-unsaturated ketones leads to unstable anions which ring open to enol ethers (80TL1515). This reaction is similar to the... 

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