Preparation of Regioselectively Protected Hydroquinones by Phosphorylation of p‐Benzoquinones with Trialkyl Phosphites

Abstract

SummaryThe title reaction has been applied to 10 monosubstituted p-benzoquinones (Scheme 2, Table). The regioselectivity of the 0-phosphorylation is influenced by bulky substituents (t-butyl and trimethylsilyl) and, electronically, by the methoxy group. The regioselectivity, which is high in nonpolar media (benzene), is lower in polar solvents (CH,Cl, and CH,CN). The synthetic potential of this transformation, exemplified by the preparation of compounds 29 (Scheme 3) and 32 (Scheme 4 ) , is considerably extended by applying milder methods for the phosphate hydrolysis and by using the reagent couple P(OCH,),/trimethylsilyl chloride, which gives clean access to p -hydroxyphenyl phosphates. p-Benzoquinones 4h and 4i with strong n-acceptor substituents react in a different way, giving phosphonates. The electronically induced regioselectivity of the 0-and C-phosphorylation is in accordance with the preferences expected for the attack by a nucleophilic phosphorylation agent.

Synthesis, spectroscopy and computational studies of some novel phosphorylated derivatives of quinoline-5,8-diones

“…However the reaction of quinones with tertiary phosphanes and phosphites is well reported in the literature and provide to variety of interesting products [19][20][21][22][23][24]. Ramirez et al [19,20,[22][23][24][25] reported the reaction of chloranil with a range of phosphorus compounds including trialkil phosphites, dialkil phosphates and triphenylphosphane to give transient red solutions from which the Fig.…”

“…Ramirez et al [19,20,[22][23][24][25] reported the reaction of chloranil with a range of phosphorus compounds including trialkil phosphites, dialkil phosphates and triphenylphosphane to give transient red solutions from which the Fig. 3.…”

Palladium-Catalyzed Insertion of 1,2- and 1,4-Quinones into Si−Si Bonds and Its Application to the Modification of Si−Si-Bond-Containing Polymers

“…The reaction of 2a using the Pd(dba) 2 −2P(OCH 2 ) 3 CEt catalyst (run 8) gave 3a (70% yield) and other products ( 4a , 5a , P1, and P2) whose GC−(HR)MS parent ions respectively corresponded to 4-(trimethylsiloxy)phenol, 1,4-bis(trimethylsiloxy)-2-(trimethylsilyl)benzene, an isomer of 3a with M + = m/z 254, and a compound with M + = m/z 434 ( 1a + 2a × 2 + Me 3 Si − H) (GC (TCD) area ratio 3a : 4a : 5a :P1:P2 = 100:10:5:5:3). Preparative GC gave relatively pure 4a (∼60% purity, a mixture with 3a ) and 5a (∼95% purity).…”