Reactions ethers

StericaHy hindered silyl ethers such as ferZ-hutyl dimethyl silyl, / fZ-butyldiphenylsilyl, and tricyclohexylsilyl have been proposed as alternatives to trityl ethers. Reaction of sucrose with 3.5 molar equivalents of ferZ-hutyl dimethyl silyl chloride produces the 6,1/6 -tri-O-silyl derivative in good yield (27). 

Bi(l,2-dithiol-3-yl) ether reactions, 6, 801 Bi( l,2-dithiol-3-ylidene) pyrolysis, 6, 794 reactions... 

The most convenient and successful synthetic preparation of octa-chlorodibenzo-p-dioxin has been described by Kulka (13). The procedure involves chlorination of pentachlorophenol in refluxing trichlorobenzene to give octachlorodibenzo-p-dioxin in 80% yield. Kulka has explained the reaction as coupling between two pentachlorophenoxy radicals. Large amounts (5—15%) of heptachlorodibenzo-p-dioxin were observed in the unpurified product. Since the pentachlorophenol used in this study contained 0.07% tetrachlorophenol, we feel that tetrachloro-phenol may be produced in situ (Reaction 4). Such a scheme would be analogous to the formation of 2,4-dichlorophenol and 3-chlorophenol produced from 2,4,4 -trichloro-2 -hydroxydiphenyl ether (Reaction 2). The solubility of octachlorodibenzo-p-dioxin was determined in various solvents data are presented in Table II. 

Primary alcohols react easily to form ethers. Reaction of methanol was carried out at 70°C using Pd(PPh3)2 (maleic anhydride) as a catalyst to give 8-methoxy-1,6-octadiene (36) (85%) accompanied by 3-methoxy-1,7-octadiene (37) (5%) and 1,3,7-octatriene (3%) (42). 

Acylation of enol ethers. Reaction of 1 with ethyl vinyl ether in ether provides an intermediate that undergoes dehydrochlorination when heated to provide the trichloromethyl ketone 2, which is converted by base (haloform reaction) to the ester 3 in high yield. 

Aryl ether Reaction conditions Product % yield... 

Arylether Sulfone Oligomers with Acetylene Termination from the Ullman Ether Reaction... 

The most convenient method of preparing the flexible (low Tg) system is to employ the Ullmann ether reaction of dibromobenzene and aromatic bis-diols followed by catalytic replacement of the bromine atoms by terminal acetylene groups. A host of commercially available bis-diols have been used in the synthesis with both meta and para dibromobenzene. Low Tg arylether oligomers have been prepared containing sulfone, sulfide, carbonyl, isopropyl and perfluoroisopropyl groups in the backbone (9). 

The reaction sequence used to synthesize these flexible systems involved four steps which are outlined in Figure 1. The first of these was an aromatic nucleophilic substitution, a polymer forming reaction in which 4,4 -dichlorodiphenyl sulfone reacts with various diols. The second step, an Ullmann ether reaction, gives bromine terminated products in which the bromines can be replaced by ethynyl end groups in the final stages. 

Polymerizations were carried out using a number of bisphenols and bisthiophenols (7a-e) with HFB (see Scheme I) and with (4a-c) the bishaloaromatics (see Scheme II). Typically, solutions equimolar (ca. 2.5M) in comonomer were treated with excess anhydrous K2CO3 and 27.7 mole % of 18-crown-6 ether. Reactions were run in a number of different solvents and at temperatures from 55 to 80 . Our results showed that polymerizations were sensitive to PTC parameters such as solvent, catalyst, and trace amounts of water in the organic phase. Under optimized conditions the expected polymers were generally obtained in excellent yields and moderately high molecular weights as evidenced by ninh measurements (see Table I). 

It is known from the preceding research that phosphorus-rich silylphosphanes or their related lithium phosphides undergo, with LiBu in ether, reactions in which a structural transformation occurs, as shown in Scheme 16 20). The reactions of the partially silylated tri- and cyclotetraphosphanes were explored in order to come closer to understanding the above reactions. It can be taken for granted that the P—C bond is not affected in such reactions. 

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