2- Trimethylsilyloxy-1,3-cyclohexadienes

Silver oxide. l-Trimethylsilyloxy-1,3-butadiene. 2-Trimethylsilyloxy-1,3-cyclohexadiene. 

Poly(p-phenylene), 5. This catalyst has been used to polymerize 1,3-butadicne with >97% 1,4-rcgioselcctivity. Attempts to polymerize phcnylcncs directly results in mixtures of para-, meta-, and orz/io-linkcd oligomers. In contrast polymerization of cis-5,6-bis(trimethy]si)yloxy)-l,3-cyclohexadiene 2 with 1 in CfcHsCI results in exclusive formation of the 1,4-poly-1,3-cyclohexadiene 3. This polymer is converted into poly(/>-phcnylene) (5) by conversion of the trimethylsilyloxy groups to acetyl groups followed by pyrolysis. 

Although commercially available, 1-trimethylsilyloxy-1,3-butadiene (1) can be easily prepared by silylation of crotonaldehyde. It has often been used as a reactive diene in Diels-Alder reactions. For example, reaction with dimethyl acetylenedicarboxylate (2) affords the cyclohexadiene diester (3) in 68% yield. This initial Diels-Alder adduct can be converted into two different aromatic products by the proper choice of conditions namely, thermal elimination affords the phthalate (4), while oxidation produces the phenol (5), hoth in good yield (eq 1). Reaction with methyl 3-nitroacrylate (6) followed hy hydrolysis of the initial adduct (7) and elimination of the -nitro group leads to the cyclohexadienol (8) (eq 2). Many other Diels-Alder reactions of this type have been carried out using (1), as shown in Table 1. In general, the endo adduct is favored, especially at lower temperatures. 

Other dienes, such as cyclohexadiene, anthracene and cyclopentadiene have also been reacted with a-oxo sulfines. The cycloaddition of a-oxo sulfines with 2-trimethylsilyloxy-1,3-butadienes afford thiacyclohexane-3-one S-oxides after hydrolysis . ... 

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