Microwave assisted synthesis of benzophenone and acetophenone ethylene ketals

Abstract

Dedicated to Professor Csaba Szántay on the occasion of his 80th birthdayAbstract A simple and convenient synthesis of acetophenone and benzophenone ethylene ketals was elaborated by performing the reaction of ethylene glycol in toluene in the presence of PTSA, under microwave irradiation with simultaneous removal of the water so formed. Under these conditions 100 % conversion and high yields were obtained within short reaction times.

Practical Synthesis of Variously Substituted 2,3,4-Benzothiadiazepine 2,2-Dioxides

“…In the course of our earlier efforts to synthesize structurally similar 2 H -1,2,3-benzothiadiazine 1,1-dioxides 12 , we used ortho -lithiation reactions of benzaldehyde acetals ( 13 , R = H), 14 and acetophenone and benzophenone ketals ( 13 , R = Me 15 16 and 13 , R = Ar, 17,18 respectively) using butyllithium to prepare ortho -chlorosulfonyl aldehyde (R = H) and ketone (R ≠ H) key intermediates 14 (Scheme 4 ).…”

“…2-(3-Chlorophenyl)-2-methyl-1,3-dioxolane 17 ( 13e ; 18.6 g, 94.0 mmol) was dissolved in THF (150 mL) under argon atmosphere and cooled to –78 °C. BuLi (60 mL of a 2.5 M solution in hexane, 0.15 mol) was added dropwise to the solution at –78 °C.…”

Synthesis and Chemistry of 1,2,3-Benzothiadiazine 1,1-Dioxide Derivatives: A Comprehensive Overview

“…An alternative route was also elaborated (Method B): treatment of acetal 15a and ketals 15b and 15c with acetohydrazide afforded sulfonylacetohydrazides 17. Removal of the 1,3-dioxolane protecting group, N-deacetylation and ring closure took place under strongly acidic conditions in one pot, giving rise to the formation of target compounds 1 [21,26] 5 [27] and 9 [25,26]. Some representatives of the 4-aryl-BTD family (5) are useful as intermediates for the preparation of disinfectants, mothproofing agents, pickling inhibitors and herbicides [17].…”

“…An alternative route was also elaborated (Method B): treatment of acetal 15a and ketals 15b and 15c with acetohydrazide afforded sulfonylacetohydrazides 17. Removal of the 1,3-dioxolane protecting group, N-deacetylation and ring closure took place under strongly acidic conditions in one pot, giving rise to the formation of target compounds 1 [21,26] 5 [27] and 9 [25,26]. A widely applicable procedure, based on ortho-lithiation methodology, has been developed at our laboratory for the synthesis of a significant variety of 4-unsubstituted, 4-aryl-and 4-alkyl-BTDs (1, 5 and 9, Scheme 4), starting from variously substituted benzaldehydes (R = H) [21] benzophenones (R = aryl) [22] or acetophenones (R = Me) [23,24] of type 10 or 11, which were masked in the first step as 1,3-dioxolanes (12, 13, Scheme 4) using microwave technology [25].…”

“…Removal of the 1,3-dioxolane protecting group, N-deacetylation and ring closure took place under strongly acidic conditions in one pot, giving rise to the formation of target compounds 1 [21,26] 5 [27] and 9 [25,26]. A widely applicable procedure, based on ortho-lithiation methodology, has been developed at our laboratory for the synthesis of a significant variety of 4-unsubstituted, 4-aryl-and 4-alkyl-BTDs (1, 5 and 9, Scheme 4), starting from variously substituted benzaldehydes (R = H) [21] benzophenones (R = aryl) [22] or acetophenones (R = Me) [23,24] of type 10 or 11, which were masked in the first step as 1,3-dioxolanes (12, 13, Scheme 4) using microwave technology [25]. Ortho-lithiation was carried out by exploiting the combined ortho-directing ability of the 1,3-dioxolan-2-yl group and another substituent of the aromatic ring, or by Br→Li exchange.…”