A Novel Synthesis of Spiro-2,5-dihydro-1,2-λ⁵-oxaphospholes Using a Three-Component Reaction

Abstract

The zwitterionic intermediate generated from dialkyl acetylenedicarboxylate and triphenylphosphine on reaction with Nsubstituted isatins leads to new highly functionalized spiro-2,5-dihydro-1,2-oxaphospholes.

Isatin derivatives in reactions with phosphorus(III–V) compounds

“…For example, it was shown that reaction of 1-substituted isatins 1e,h,p-r with triphenylphosphine in the presence of acetylenedicarboxylic esters produced high yields of γ-spirolactones 103, containing an indolinone fragment. [110][111][112] The interaction of acetylenedicarboxylate and triphenylphosphine initially gave the bipolar ion D, the anionic part of which readily attacked the carbonyl group of isatin, forming zwitterion E. The latter underwent an intramolecular attack by alkoxide ion on the carbonyl group, followed by elimination of triphenylphosphine (bipolar ions F and G) (Scheme 48).…”

“…Thus, the bipolar ionic intermediate attacked the more acidic proton at the nitrogen atom, which was absent in the N-substituted isatin derivatives described above. [110][111][112][113]118 Trialkylphosphite initially reacted with acetylenedicarboxylate and gave the zwitterionic intermediate M, which added to isatin, and the adduct was hydrolyzed during the chromatographic separation of reaction products (Scheme 53). We should also mention within this review a work 120 describing the reaction of isatin (1a) with triphenylphosphine in the presence of metal chloride.…”

Synthesis of 5-(Trifluoromethyl)-2,5-dihydro-1,2λ5-oxaphospholes by a One-Pot Three-Component Reaction

“…As early as 1961, Tebby and co-workers found that the addition of triphenylphosphine to various activated alkynes, such as 1,4-diphenylbut-2-yne-1,4-dione, but-2-ynedinitrile, or dimethyl acetylenedicarboxylate, gave zwitterionic intermediates. 7,8 Recently, groups led by Esmaeili 9 and by Yavari 10 have reported that the reactions of acetylenic compound with triphenylphosphine in the presence of ketones give the corresponding 2,5-dihydro-1,2-oxaphospholes. However, to the best of our knowledge, there are few reports of preparations of fluorinated oxaphos-pholes.…”