One‐Pot Diastereoselective Synthesis of Densely Functionalized 2H‐Indeno[2,1‐b]furans. Single‐Crystal X‐Ray Structure of Dimethyl 8,8a‐Dihydro‐8‐oxo‐8a‐(2,2,2‐trichloroethoxy)‐2H‐indeno[2,1‐b]furan‐2,3‐di­carboxylate

Abstract

Highly reactive 1 : 1 intermediates were produced in the reaction of Ph 3 P and dialkyl acetylenedicarboxylates (¼ dialkyl but-2-ynedioates). Protonation of these intermediates by alcohols (2,2,2trichloroethanol, 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-indeno[2,1-b]furan-2,3-dicarboxylate (10a) was established by a single-crystal X-ray structure determination, establishing that the one-pot multicomponent condensation reaction was completely diastereoselective.Introduction. -Compounds with an ideno[2,1-b]furan or -pyrrole skeleton have attracted interest in bioorganic, natural-products, and medicinal chemistry. They show pharmaceutical and biological activities including antimicrobial and antifungal effects [1 -4].For years, acetylenic esters have attracted the attention of organic chemists, mostly as Michael acceptors [5]. In recent years, there has been an increasing interest on the applications of acetylenic esters in multicomponent syntheses [5] [6], specially for preparing stabilized phosphonium ylides [7 -13]. Due to atom economy, convergent character, and simplicity of one-pot procedures, multicomponent condensation reactions have great potentials in synthesis. The development of novel multicomponent condensation reactions is also receiving growing interest from industrial-chemistry research groups, and represents a challenge for organic chemists [5] [6].Based on our literature survey, only few methods have been reported in the literature for the synthesis of 2H-indeno[2,1-b]furans [2] [3]. These protocols are multi-step in nature reports on the synthesis of 2H-indeno[2,1-b]furans are fairly rare [2] [3].In the past, we have established a convenient one-pot method for preparing stabilized phosphonium ylides utilizing in situ generation of the phosphonium salts [8 -13]. As part of our ongoing program to develop efficient and robust methods for the

Silica Gel Promotes Cascade Synthesis of 2-(Heteroaryl)acetamide Derivatives from Isocyanides, Dialkylamines, and Heteroarylcarbaldehydes

“…Its ease of workup and good yields makes it a useful addition to modern synthetic methodologies. [44][45][46][47][48][49][50][51][52][53][54][55] EXPERIMENTAL Starting materials and solvents were obtained from Merck (Germany) and Fluka (Switzerland) and were used without further purification. The methods used to follow the reactions were TLC and NMR.…”

The reaction of (N‐isocyanimino) triphenylphosphorane with (E)‐3‐aryl‐2‐ propenoic acid derivatives: One‐pot synthesis of 2‐[(E)‐2‐aryl‐1‐ethenyl]‐1,3,4‐oxadiazoles via intramolecular aza‐Wittig reaction

“…The (N-isocyanimino)triphenylphosphorane 2 is expected to have unique synthetic potential because it provides a reaction system in which the iminophosphorane group can react with a reagent having a carbonyl functionality [4,5]. In recent years, we have established a one-pot method for the synthesis of organophosphorus compounds [6][7][8][9][10][11][12]. As a part of our ongoing program to develop efficient and robust methods for the preparation of heterocyclic compounds [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], we sought to develop a convenient preparation of 2-[(E)-2-aryl-1-ethenyl]-1,3,4-oxadiazole 3 from (E)-3-aryl-2-propenoic acid derivatives 1 and (Nisocyanimino)triphenylphosphorane 2 in fairly good yield in neutral conditions.…”

The Reaction of N-Isocyaniminotriphenylphosphorane with 2-Oxopropylbenzoate (or 4-Bromobenzoate) and a Primary Amine in the Presence of (E)-Cinnamic Acid Derivatives: A One-Pot Efficient Four-Component Reaction for the Synthesis of 2-(Arylamino)-2-(5-aryl

“…In recent years, we have established a one‐pot method for the synthesis of organophosphorus compounds . As part of our ongoing program to develop efficient and robust methods for the preparation of heterocyclic compounds , we wish to report the synthesis of a disubstituted 1,3,4‐oxadiazole derivatives 7 by a four‐component condensation of N ‐isocyaniminotriphenylphosphorane 6 with 2‐oxopropylbenzoate (or 2‐oxopropyl 4‐bromobenzoate) in the presence of ( E )‐cinnamic acids and primary amines (Scheme ).…”