Hypervalent Iodine/Triflate Hybrid Benzdiyne Equivalents: Access to Controlled Synthesis of Polycyclic Aromatic Compounds.

The 1,4-benzdiyne equvalent, [2,5-bis(trimethylsilyl)-4-(trifyloxy)phenyl](phenyl)iodonium triflate, was prepared from sodium 2,4,5-trichlorophenoxide. The chemoselective generation of an aryne from the side of the phenyliodonio group was observed after treatment with a fluoride ion. Double cycloaddition of 1,4-benzdiyne with different arynophiles was conducted in one pot, giving bis-cycloadducts in high yields. Similarly, the 1,3-benzdiyne equivalent bearing phenyliodonio and triflate groups was prepared from sodium 2,3,6-trichlorophenoxide. The 1,3-benzdiyne equivalent also underwent the chemoselective stepwise generation of arynes and the double cycloaddition with different arynophiles. These hybrid benzdiyne equivalents provided the double cycloadducts in high yields and enabled the convenient one-pot procedure for synthesis of polycyclic aromatic compounds.

Palladium-Catalyzed Desilylative Acyloxylation of Silicon-Carbon Bonds on (Trimethylsilyl)arenes: Synthesis of Phenol Derivatives from Trimethylsilylarenes.

A strategy for desilylative acetoxylation of (trimethylsilyl)arenes has been developed in which (trimethylsilyl)arenes are converted into acetoxyarenes. The direct acetoxylation is performed in the presence of 5 mol % of Pd(OAc)2 and PhI(OCOCF3)2 (1.5 equiv) in AcOH at 80 °C for 17 h. The acetoxyarenes are obtained in good to high yields (67-98%). The synthetic utility is demonstrated with a one-pot transformation of (trimethylsilyl)arenes to phenols by successive acetoxylation and hydrolysis. Furthermore, desilylative acyloxylation of 2-(trimethylsilyl)naphthalene using several carboxylic acids has been conducted.

Synthesis of 1,2-bis(trimethylsilyl)benzene derivatives from 1,2-dichlorobenzenes using a hybrid metal Mg/CuCl in the presence of LiCl in 1,3-dimethyl-2-imidazolidinone.

A practical and safe synthesis of 1,2-bis(trimethylsilyl)benzene from 1,2-dichlorobenzene and Me3SiCl was achieved by use of a hybrid metal of Mg and CuCl in the presence of LiCl in 1,3-dimethyl-2-imidazolidinone (DMI). This method does not require a toxic HMPA, provides a high yield of the product under mild conditions, and is also applied to synthesis of substituted 1,2-bis(trimethylsilyl)benzenes and poly(trimethylsilyl)benzenes.

Reaction of iodonium ylides of 1,3-dicarbonyl compounds with HF reagents.

Reaction of dibenzoylmethane with (diacetoxyiodo)benzene in the presence of KOH in MeCN quantitatively gave the corresponding iodonium ylide, which was treated with a HF reagent to afford the corresponding 2-fluorinated dibenzoylmethane in 14-50% yields. The similar reaction of the iodonium ylides obtained from 1-phenylbutan-1,3-dione, ethyl benzoylacetate, and ethyl p-nitrobenzoylacetate with TEA·3HF gave the corresponding fluorinated products in 17-34% yields. It is suggested that the fluorinated products were formed through the C-protonation of the ylide, followed by displacement with fluoride ion. The same reaction of the iodonium ylide of dibenzoylmethane with concentrated HCl gave the corresponding chlorinated product in 45% yield.