Henry Condensation Research Articles

Nitroalkenes as precursors to the aromatic spiroketal skeleton of γ-rubromycin. A Nef-type reaction mediated by Pearlman's catalyst

The first synthesis of the benzannelated spiroketal core of γ-rubromycin using Henry condensations and a novel Nef-type reaction induced by Pearlman's catalyst is described.

ChemInform Abstract: C‐Glycoside Syntheses. Part 2. Henry Condensations of 4,6‐O‐Alkylidene Pyranoses with a 1,3‐Proton Transfer Catalyst ‐ A Route to Blocked Aminomethyl‐C‐glycosides.

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C-glycoside synthesis II: Henry condensations of 4,6-O-alkylidene pyranoses with a 1,3-proton transfer catalyst- a route to blocked aminomethyl-C-glycosides.

In the presence of a novel 1,3-proton transfer catalyst (2-hydroxypyridine (2-HP)/ 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)/ molecular sieves), 4,6-O-benzylidene-D-glucopyranose (1),4,6-O-isopropylidene-D-mannose (12), and 4,6-O-isopropylidene-D-glucose (16) undergo Henry condensations with nitromethane in THF to give acetal protected nitromethyl C-glycopyranosides (2, 13, and 17, respectively), which were characterized as their O-acetyl derivatives (5, 15, and 18, respectively). The Henry product from 4,6-O-benzylidene-Dglucopyranose could be reduced, with retention of the 4,6-O-benzylidene protecting group, by a specially prepared form of elemental iron in aqueous tetrahydrofuran under CO2 to aminomethyl-C-glycopyranoside (16), characterized as N-acetyl, peracetyl, and N-Cbz derivatives (7, 8, 9, 10), and converted with diazonium salt to a triazene derivative (II). Nitroalkenes are only mechanistic intermediates in our condensations with nitromethane, but they undergo Michael additions with a second mole of nitromethane to give novel 5,7-O-alkylidene-1,2-deoxy-1 nitro-2-nitromethyl-D-heptitols (3 and 14) as side-products.

Henry condensation under high pressure 2. Effect of aromatic aldehyde type and pressure on the yield of ?-nitrostyrenes and secondary processes

Condensation of aromatic aldehydes (I)-(XX) with EtNO2 and n-PrNO2 in AcOH in the presence of AcONH4 or i-BuNH2 gives primarilyω-nitrostyrenes (Ia, b)-(XXa, b) and small quantities of nitriles (Ic)-(XXc), oximes (Id)-(XXd), and ketones (Ie, f)-(XXe, f). The yields of (Ia, b)-(XXa, b) at P=1 atm are higher for acceptor substituents on the aromatic ring whereas at P=10 kbar, they are higher for donor substituents. High pressures suppress the formation of (Ic-f)-(XXc-f) and the Z-isomers of (Ia, b)-(XXa, b). The high pressure technique is especially useful in the preparation of donor-substituted (Ia, b)-(XXa, b) which are intermediates in the synthesis of the psychotropic β-phenylethylamines.

Henry condensation at high pressures

The hitherto inaccessible nitroolefin (VII), which is the most convenient intermediate for the synthesis of the psychotropic amine (VIII), has been obtained by the direct condensation at high pressures (up to 1500 MPa) of piperonal (V) with 1-nitropropane (VI). The structure of (VII) was confirmed by direct synthesis from pyrocatechol (X). The amine (VIII) was obtained in three steps from (VII). This synthesis of (VIII) is shorter than that previously reported.

ChemInform Abstract: AN IONIC CHAIN MECHANISM FOR THE SUBSTITUTION OF AN ACETATE GROUP BY THE 2‐NITROPROPAN‐2‐IDE ION IN BENZYLIDENE DIACETATES

AbstractDer Mechanismus der Reaktion von Arylmethylendiacetaten (I) mit dem Propanid (II) zu Nitroalkylacetaten (III) wird diskutiert.

An ionic chain mechanism for the substitution of an acetate group by the 2-Nitropropan-2-ide ion in benzylidene diacetates

The reaction of 16 arylmethylene diacetates [benzylidene diacetates; ArCH(OAc)2] with lithium 2-nitropropan-2-ide in dimethyl sulphoxide has been studied. With the exception of aryl rings bearing strongly electron-donating substituents a ready reaction takes place giving l-aryl-2-methyl-2-nitropropyl acetates in good yield. The mechanism of this reaction, in which an acetate group is formally substituted by a (CH3)2C(N02) group, has been shown to be an ionic chain mechanisminvolving nucleophilic cleavage of the diacetate to catalytic quantities of the corresponding arene carbaldehyde (ArCHO) which subsequently undergoes a Henry condensation followed by a transacetylation reaction. In some cases (nitro heteroaromatic derivatives) a subsequent elimination reaction gives enol-acetates [ArC(OAc)=C(CH3)2].

Synthesis of some model ?-fluoro-?-nitrodiols and their acetates

Someβ-fluoro-β-nitrodiols were obtained by the fluorination of aqueous solutions of the corresponding nitronate salts of the diols with elemental fluorine and by the Henry condensation.