Highly reactive 1 : 1 intermediates were produced in the reaction of Ph3P and dialkyl acetylenedi-
carboxylates (¼dialkyl but-2-ynedioates). Protonation of these intermediates by alcohols (2,2,2-
trichloroethanol, propargyl alcohol (¼ prop-2-yn-1-ol), MeOH, benzyl alcohol, and allyl alcohol
(¼ prop-2-en-1-ol) led to vinyltriphenylphosphonium salts 4, which underwent a Michael addition
reaction with the conjugate base to produce the corresponding stabilized phosphonium ylides 5
(Scheme). Wittig reaction of the stabilized phosphonium ylides with ninhydrin (6) led to the
corresponding densely functionalized 2H-indeno[2,1-b]furans 10 in fairly good yields (Table 1). The
structures of the final products were confirmed by IR,
1
H- and 13
C-NMR spectroscopy, and mass
spectrometry. The configuration of dimethyl 8,8a-dihydro-8-oxo-8a-(2,2,2-trichloroethoxy)-2H-in-
deno[2,1-b]furan-2,3-dicarboxylate (10a) was established by a single-crystal X-ray structure determi-
nation, establishing that the one-pot multicomponent condensation reaction was completely diaster-
eoselective.
