Regioselective Synthesis of 5-Alkylsalicylates, 5-Alkyl-2-hydroxy-acetophenones, and 5-Alkyl-2-hydroxy-benzophenones by [3 + 3] Cyclization of 1,3-Bis(silyl enol ethers) with 2-Alkyl-1,1,3,3-tetraethoxypropanes

Abstract

A variety of 5-alkylsalicylates, 5-alkyl-2-hydroxy-acetophenones, and 5-alkyl-2-hydroxy-benzophenones was regioselectively prepared by TiCl4 mediated formal [3 + 3] cyclization of 1,3-bis(silyl enol ethers) with 2-alkyl-1,1,3,3-tetraethoxypropanes.

Diversity‐Oriented Synthesis of Chlorinated Arenes by One‐Pot Cyclizations of 4‐Chloro‐1,3‐bis(trimethylsilyloxy)buta‐1,3‐dienes

“…The structure of 13a was independently confirmed by X-ray crystal structure analysis (Figure 4). [32] Chan et al were the first to report TiCl 4 -mediated cyclizations between 1,3-bis(silyloxy)buta-1,3-dienes and 1,1,3,3-tetramethoxypropane (14a), [26] whereas we have reported [35] TiCl 4 -mediated cyclizations between 1,3-bis(silyloxy)buta-1,3-dienes and the 1,1,3,3-tetraethoxypropanes 14b-e, which are available in three steps by a known protocol. [36] TiCl 4 -mediated cyclizations between the chlorinated diene 3a and 14a-e afforded the 3-chlorosalicylates 15a-e (Scheme 10, Table 6).…”

Nickel-Catalyzed Decarbonyloxidation of 3-Aryl Benzofuran-2(3H)-ones to 2-Hydroxybenzophenones

“…(2-Hydroxy-5-methylphenyl)(phenyl)methanone (2a). 28 The representative general procedure mentioned above was followed. Purification by PTLC on silica gel (petroleum ether/ethyl acetate = 200/1) yielded the title compound 2a in 99% (42.0 mg) as a yellow solid; mp, 70−73 °C; reported mp, 81 °C; R f = 0.35 (petroleum ether/ ethyl acetate = 200/1).…”

Regioselective Synthesis of 2-(Arylthio)benzoates by the First Catalytic [3+3] Cyclocondensations of 3-(Arylthio)-1-(trimethylsilyloxy)-1,3-butadienes with 1,1,3,3-Tetramethoxypropane

“…The TiCl 4 -mediated cyclocondensation of 1,3-bis(silyloxy)-1,3-butadienes with 1,1,3,3tetramethoxypropane and 2-alkyl-1,1,3,3-tetraethoxypropanes has also been reported. 12,13 Recently, we have developed a catalytic variant of this reaction using trimethylsilyl trifluoromethanesulfonate (TMSOTf) as the catalyst. 14 Chan et al reported the synthesis of 2-(phenylthio)benzoates by TiCl 4 -mediated [3+3] cyclization of 3-(silyloxy)-2-en-1-ones with 3-(arylthio)-1-(trimethylsilyloxy)-1,3-butadienes.…”