Methanolysis (solvolysis) and synthesis of 4′-substituted 4-benzyloxybenzyl chlorides and some related compounds: comparisons with the corresponding benzoyl compounds

Abstract

The kinetics of methanolysis (solvolysis) in 97.4% MeOH-dioxan of a series of 4'-substituted 4-benzyloxybenzyl chlorides, and of 4-anisy1, 4-phenoxybenzy1, and benzyl chlorides have been studied and discussed, including comparisons with the data for the corresponding series of benzoyl chlorides, previously reported by us. The 4'substituted precursor alcohols, chlorides, and product methyl ethers are all new compounds. 4-Anisyl chloride and the series of benzyloxybenzyl chlorides react by the S, 1 mechanism, whereas benzyl chloride reacts by the S,2 mechanism. 4-Phenoxybenzyl chloride shows intermediate behaviour. A similar pattern was observed with the corresponding benzoyl compounds. In both series the reactivity order is CH,O > 4'-CH,C,H4CH,0 (-0.76) >C,H5CH,0 (-0.74) 7 4'-CIC,H4CH20 (-0.69) > 4'-N02C,H4CH,0 (-0.60) > C6H50 > H (values in parentheses are new IS+ values). At 25" the overall range of rates is 4 290 in the benzyl series, compared with only 2.42 in the benzyl series. The Arrhenius parameters in the two series demonstrate, however, an underlying simil

Reatividade Relativa em Solvólise Nucleofílica de Cloretos de Arilsulfenila, Arilcarbonila, Arilsulfonila, Arilmetila e de Arila

“…Algumas comparações entre as reatividades dos carbonos: aromático e saturado, carbonílico e saturado, aromático e carbonílico, aromático, heteroaromático e sistema tropílico, carbonílico e imidoílico, e de arenos coordenados e não-coordenados são descritas na literatura [6][7][8][9][10][11][12][13][14][15] . Todavia, muito pouco é conhecido acerca da reatividade do enxofre como centro eletrofílico, embora haja uma quantidade razoável de trabalhos sobre centros sulfonílicos 16 e pouco sobre centros sulfenílicos.…”

“…Julgou-se, também, que entre as classes de compostos estudados, aquelas que oferecem maiores chances de operar por um mecanismo unimolecular são os sistemas benzílico e benzoílico. Entretanto, é muito relevante o fato de ter-se constatado que, mesmo na metanólise, nem cloreto de benzila e nem de benzoíla reagiu por um mecanismo S N 1 11,17 . Escolheram-se sistemas arílicos por conveniência e porque planejou-se estender os estudos cinéticos para incluir arenos eletrofí-licos.…”

Regioselective synthesis of spiro quinazolinones via sequential hydroalkoxylation and intramolecular amide-cyclization of alkynol ureas

“…This latency in the reaction period can be attributed to the destabilization of the benzylic vinyl carbocation A by the electron-withdrawing groups during the transformation (Scheme 4). 14 To account for the steric congestion, a di-substituted methyl substituent was incorporated in the ring, which delivered its corresponding product 2k in 89% yield. Next, altering the “R 2 ” group with a phenyl substituent resulted in the products 2l–2n in excellent yields.…”

Functionalized Deep-Cavity Cavitands

“…deep-cavity cavitand yield a (%) does it occur via a double S N 2 mechanism or a process whereby the second step is an S N 1 mechanism on an oxonium intermediate? Furthermore, as is observed for a variety of solvolyses of different benzyl halides or sulfonates, [31][32][33] the precise mechanism of benzal bridging is likely to be dictated by the aromatic ring's substituents.…”

“…Rationalization of these results is complicated by a lack of understanding of the bridging mechanism in general; does it occur via a double S N 2 mechanism or a process whereby the second step is an S N 1 mechanism on an oxonium intermediate? Furthermore, as is observed for a variety of solvolyses of different benzyl halides or sulfonates, − the precise mechanism of benzal bridging is likely to be dictated by the aromatic ring's substituents. Unfortunately therefore, the above data offer little opportunity for gleaning mechanistic details of bridging reactions in general.…”