Thank you GC_MS. May I tempt you with this one;
Tetrahedron, 52, 1677-1684 (1996)Nitroaldol (Henry) reaction catalyzed by Amberlyst A-21 as a far superior heterogenous catalyst...We found that Amberlyst A-21 is far superior as general catalyst for the nitroaldol reaction [1], in fact it is possible to obtain
beta-nitroalkanols in high yields (70-95%), by limited reaction times, and from a wide variety of starting materials. The Amberlyst A-21 avoids the dehydration of the 2-nitroalcohols into nitroalkenes even if aromatic aldehydes are used.
The reaction has been performed by adding 8-10 g of Amberlyst A-21 to 50 mmol of aldehyde and 50 mmol of nitroalkane, however, unlkie other methods the yields are substantially independent from the ratio catalyst/starting materials. It is important to point out that, after recycling, the catalyst can be reused withouta considerable loss of efficiency. Different solvents can be used (Et
2O, CH
2Cl
2, THF) without a substantial change of the yield.
By our method both primary and secondary nitroalkanes gives god results. Compared to other processes our procedure gives, generally, better yields. Moreover, this catalyst does not affect labile funtional groups and its mildness is demonstrated by the stablilty of the bromohydrin to epoxide formation, under basic conditions.
General procedure for the synthesis of nitroalcohols, without solvent.A 100 ml two-necked flask equipped with a mechanical stirrer was charged with the nitro compound (30 mmol) and cooled with an ice-water bath. The aldehyde (30 mmol) was added, and the mixture was stirred for 15 minutes. Amberlyst A-21 (5-7 g) was added, and stirring cotinued for the right time. The Amberlyst was washed with CH
2Cl
2 (4 x 25 ml). The filtered extract was evaporated and the crude nitroalcohol was purified by chromatography or used as it is.
General procedure for the synthesis of nitroalcohols, with solvent.The nitro compound (30 mmol) and the aldehyde (30 mmol) were added to the solvent (30 ml), then Amberlyst A-21 (5-7 g) was added and the mixture was magnetically stirred for the right time. After filtration the Amberlyst was washed with the solvent used and the extracts were evaporated. The crude nitroalcohol was purified as above.
[1] From
J. Chem. Soc., Perkin Trans. 1, 107-110 (1999)...The utilisation of Amberlyst A-21 proved to be not very efficient in our hands. Instead of Amberlyst A-21, Amberlite IRA-420 (OH-form) or DOWEX-1 (OH-form) can be used.
Barium´s voice In this article the authors first converted benzyl alcohol, p-MeO-benzyl alcohol, p-NO2-benzyl alcohol, p-F-benzyl alcohol and o-F-benzyl alcohol to the benzaldehydes by oxidation using polymer supported permanganate (PSM) [2], then the benzaldehydes were condesed with either nitromethane or nitroethene (a large excess of nitroalkane, serving as solvent and reagent, was used) to the corresponding
beta-nitroalcohols using either Amberlite IRA-420 or DOWEX-1. Immediately after that the nitroalkenes were formed by esterifying the alcohols with trifluoroacetic acid in DCM, then the nitrostyrenes was formed by reaction with triethylamine.
[2] Polymer supported permanganate (PSM) was prepared by filtering an aqueous solution of potassium permanganate through Amberlyst A-27, subsequent washing of the obtined brick-red material with water and acetone and drying of the beads
in vacuo.
Benzyl achohol --> benzaldehyde (95%) -->
beta-nitrostyrene (27%)
p-MeO-Benzyl achohol --> p-MeO-benzaldehyde (95%) --> p-MeO-
beta-nitrostyrene (23%), p-MeO-
beta-methyl
-beta-nitrostyrene (25%)
p-NO
2-Benzyl achohol --> p-NO
2-benzaldehyde (95%) --> p-NO
2-
beta-nitrostyrene (45%), p-NO
2-
beta-methyl
-beta-nitrostyrene (77%)
p-F-Benzyl achohol --> p-F-benzaldehyde (95%) --> p-F-
beta-nitrostyrene (60%)
o-F-Benzyl achohol --> o-F-benzaldehyde (95%) --> o-F-
beta-nitrostyrene (65%)
No experimental procedures was given by the assholes