Microwave-assisted InCl3-catalyzed Meyer–Schuster rearrangement of propargylic aryl carbinols in aqueous media: a green approach to α,β-unsaturated carbonyl compounds

One-Pot Synthesis of Push–Pull Butadienes from 1,3-Diethyl-2-thiobarbituric Acid and Propargylic Alcohols

A new synthetic procedure for obtaining two previously reported donor-acceptor butadiene dyes, namely 5-(3,3-bis(4-methoxyphenyl)allylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione and 5-(3,3-bis(4-(dimethylamino)phenyl)allylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione, based on the InCl3-catalyzed coupling 1,3-diethyl-2-thiobarbituric acid with 1,1-bis(4-methoxyphenyl)prop-2-yn-1-ol and 1,1-bis(4-(dimethylamino)phenyl)prop-2-yn-1-ol, respectively, is presented. The reactions, which cleanly proceed in water under MW irradiation, involve the initial generation of the corresponding enals by Meyer-Schuster rearrangement of the alkynols and their subsequent Knoevenagel condensation with the 2-thiobarbituric acid derivative. By following the same approach, the novel butadiene 5-(3,3-bi([1,1′-biphenyl]-4-yl)allylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione, which was characterized by 1H and 13C{1H} NMR, IR, UV-Vis, elemental analysis and HRMS, was synthesized in 79% yield.

Electrophilic halogenations of propargyl alcohols: paths to α-haloenones, β-haloenones and mixed β,β-dihaloenones

The Meyer–Schuster rearrangement of propargyl alcohols or alkynols leading to α,β-unsaturated carbonyl compounds is well known. Yet, electrophilic halogenations of the same alkynols and their alkoxy, ester and halo derivatives are inconspicuous. This review on the halogenation reactions of propargyl alcohols and derivatives intends to give a perspective from its humble direct halogenation beginning to the present involving metal catalysis. The halogenation products of propargyl alcohols include α-fluoroenones, α-chloroenones, α-bromoenones and α-iodoenones, as well as β-haloenones and symmetrical and mixed β,β-dihaloenones. They are, in essence, tri and tetrasubstituted alkenes carrying halo-functionalization at the α- or β-carbon. This is a potential stepping stone for further construction towards challenging substituted alkenones via Pd-catalysed coupling reactions.

This review highlights the development of α-haloenone, β-haloenone and mixed β,β-dihaloenone formations from propargyl alcohols via direct electrophilic halogenations and metal catalysed-halonium interception rearrangements.

Deep eutectic solvent-catalyzed Meyer-Schuster rearrangement of propargylic alcohols under mild and bench reaction conditions

The Meyer-Schuster rearrangement of propargylic alcohols into α,β-unsaturated carbonyl compounds has been revisited by setting up an atom-economic process catalyzed by a deep eutectic solvent FeCl3·6H2O/glycerol. Isomerizations take place smoothly, at room temperature, under air and with short reaction times. The unique solubilizing properties of the eutectic mixture enabled the use of a substrate concentration up to 1.0 M with the medium being recycled up to ten runs without any loss of catalytic activity.

Butadiene dyes based on 3-(dicyanomethylidene)indan-1-one and 1,3-bis(dicyanomethylidene)indane: synthesis, characterization and solvatochromic behaviour

Novel 1,1-diaryl-substituted butadiene dyes containing 3-(dicyanomethylidene)indan-1-one and 1,3-bis(dicyanomethylidene)indane have been synthetized, and their light absorption and solvatochromic properties evaluated.

New Ag(I)-iminophosphorane coordination polymers as efficient catalysts precursors for the MW-assisted Meyer-Schuster rearrangement of propargylic alcohols in water

Treatment of the N-thiophosphorylated iminophosphorane ligands (PTA)═NP(═S)(OR)2 [PTA = 1,3,5-triaza-7-phosphaadamantane, 3a and 3b] and (DAPTA)═NP(═S)(OR)2 [DAPTA = 3,7-diacetyl-1,3,7-triaza-5-bicyclo[3.3.1]nonane, 4a and 4b] with an equimolecular amount of AgSbF6 leads to high-yield formation of the new one-dimensional coordination polymers [Ag{μ(2)-N,S-(PTA)═NP(═S)(OR)2}]x[SbF6]x (5a and 5b) and [Ag{μ(2)-O,S-(DAPTA)═NP(═S)(OR)2}]x[SbF6]x (6a and 6b), respectively. These new (iminophosphorane)silver(I) coordination polymers are efficient catalyst precursors for the Meyer-Schuster isomerization of both terminal and internal alkynols. Reactions proceeded in water, under aerobic conditions and using microwave irradiation as heating source, to afford the corresponding α,β-unsaturated carbonyl compounds in excellent yields, without the addition of any cocatalyst. Remarkably, it should be noted that this catalytic system can be recycled up to 10 consecutive runs (1st cycle 45 min, 99%; 10th cycle 6 h, 97%). ESI-MS analysis of 5a in water has been carried out providing valuable insight into the monomeric active species responsible for catalytic activity in water.