Cesium carbonate mediated exclusive dialkylation of active methylene compounds

Abstract

Active methylene compounds are regioselectively dialkylated by variety of alkyl halides using cesium carbonate in quantitative yield. The reaction yielded exclusively dialkylated products with no intermediate monoalkyaltion or mixture of products.

Modular synthesis of oligoacetylacetones via site-selective silylation of acetylacetone derivatives

“…Therefore, these reaction conditions were applied for other 3,3disubstituted acetylacetone analogues 1b-d those could be obtained through direct substitution from acetylacetone in high yields. [10][11][12] While 1,1-diacetylcyclohexane (1b) was converted to enol silyl ether 2b in 90% yield under the similar conditions, reaction with 1,1-diacetylcyclopropane (1c) resulted in formation of a mixture of mono-and bis-silylated products 2c and 2'c (78:16, NMR ratio), along with 6% of starting material 1c. Because of hydrolysis on silica gel, 2c was isolated in 51% yield.…”

Palladium-Catalyzed Hydroboration/Cyclization of 1,n-Dienes

“…1,2-Dichloroethane was purchased from Kanto Chemical Co., Inc. and distilled from P 2 O 5 . Diene substrate 1c , 1d , 1h , 1i , 1j , 1k , and 6a – c were prepared according to the literature. Diene ( E )-1i was synthesized from ( E )-crotyl bromide using a procedure similar to the one for the preparation of 1i , and the analytical data were in accordance with the literature .…”

Novel one-pot synthesis of a library of 2-aryloxy-1,4-naphthoquinone derivatives. Determination of antifungal and antibacterial activity

“…The preference of Cs 2 CO 3 over CsOH rests on two criteria: (1) the former's lower hygroscopic character; even a trace of water produced subproducts due to attack on C2 in the naphthoquinone moiety to form lawsone, and (2) because carbonate is a weaker base with negligible nucleophilic character, compared to hydroxide ion. [60][61][62] On the other hand, Al 2 O 3 /KF was reserved to the most acidic phenols. Although the pK a of HF is low (pK a ¼ 3.14), it is suspected that KOH is produced in the early stages of deposition of KF over alumina, hence augmenting the basicity of the resulting material without the concomitant production of free hydroxide ion.…”

“…The elution was perform using an isocratic ow of 1 mL min À1 and total elution time of 25 minutes. The wavelengths used were 269 nm (36-45, 48, 49, 52, 53, 55-58, 62, 63), 274 nm (34,51,60) and 286 nm (35,46,47,54,59,61). MeCN (100%) was used as eluent at 269 nm and 274 nm, and a mixture of 40% water/methanol at 286 nm.…”