Unusual Reactivity of Aryl Aldehydes with Triethyl Phosphite and Zinc Bromide: A Facile Preparation of Epoxides, Benzisoxazoles, and α‐Hydroxy Phosphonate Esters

Abstract

A facile preparation of trans‐epoxides was achieved by a (EtO)3P–ZnBr2‐mediated deoxygenation reaction of the corresponding 2‐nitrobenzaldehydes. The sterically hindered analogues of 2‐nitrobenzaldehyde underwent a reaction with triethyl phosphite in the presence of ZnBr2 as the catalyst to form benzisoxazoles as the sole product. Under identical conditions, the reactions of electron‐rich as well as moderately electron‐deficient aryl aldehydes furnished the corresponding α‐hydroxy phosphonate esters.

Amakusamine from a Psammocinia sp. Sponge: Isolation, Synthesis, and SAR Study on the Inhibition of RANKL-Induced Formation of Multinuclear Osteoclasts

“…Desired 4,7-dibromo-6-nitropiperonal ( 5 , 1.7 g, 63%) was obtained as a pale yellow solid. All spectroscopic data of 5 were identical with reported data …”

“…All spectroscopic data of 5 were identical with reported data. 27 To a solution of 4,7-dibromo-6-nitropiperonal (5, 1.95 g, 5.5 mmol) in nitromethane (24 mL) was added Al 2 O 3 (1.7 g, 16.7 mmol) at rt under an Ar atmosphere. The reaction mixture was stirred for 12 h at rt.…”

Synthesis of Epoxides from Alkyl Bromides and Alcohols with in Situ Generation of Dimethyl Sulfonium Ylide in DMSO Oxidations

“…These substrates proved to be amenable to the reaction, giving 2b – e in 60–81% yields. The p -nitrobenzyl bromide 1f gave the unexpected cis epoxide 2f in a lower yield (33%) . The reaction of fully substituted 2,3,5,6-tetrafluoro-4-methylbenzyl bromide 1g also proceeded smoothyl to give trans 2g in 64% yield.…”

Synthesis and Reactions of α-Hydroxyphosphonates

“…However, in the second case, the desired products were only formed in traces. Metal salts were also applied in the reaction of oxo compounds and trialkyl phosphites with success ( Table 2 /Entries 12–14) [ 52 , 53 , 54 ]. The reaction of slightly electron-rich benzaldehydes and triethyl phosphite in the presence of ZnBr 2 afforded the corresponding α-hydroxyphosphonates ( Table 2 /Entry 12) [ 52 ].…”

“…Metal salts were also applied in the reaction of oxo compounds and trialkyl phosphites with success ( Table 2 /Entries 12–14) [ 52 , 53 , 54 ]. The reaction of slightly electron-rich benzaldehydes and triethyl phosphite in the presence of ZnBr 2 afforded the corresponding α-hydroxyphosphonates ( Table 2 /Entry 12) [ 52 ]. Bismuth(III) nitrate pentahydrate was applied efficiently as the catalyst in the reaction of aldehydes and triethyl phosphite under MW irradiation at 70 °C ( Table 2 /Entry 13) [ 53 ], while the niobium(V)chloride-trimethylsilyl chloride system was used in an amount of only 0.05 mol % at 25 °C to prepare hydroxyphosphonates ( Table 2 /Entry 14) [ 54 ].…”