Here is another procedure that should definately give piperonal from piperine. It also gives benzaldehyde from cinnamaldehyde.
Foxy
Bis(2,2'-bipyridyl)copper(II) permanganate (BBCP): A mild and versatile oxidant in organic synthesis
Tetrahedron, Volume 40, Issue 23, 1984, Pages 5001-5004
H. Firouzabadi, , A. R. Sardarian, M. Naderi and B. Vessal
Abstract
The preparation of bis(2,2'-bipyridyl)copper(II) permanganate (BBCP) is described. The reagent converts alcohols to the corresponding carbonyl compounds, -hydroxy ketones to diketones, hydroquinone to p-benzoquinone, and compounds with benzylic double bonds to benzaldehyde in high yield. Benzophenone oxime, acetophenone oxime and various benzaldoximes are converted to the corresponding carbonyl compounds, aromatic amines to azo compounds, and benzylamine to benzaldehyde, usually in high yields, under mild condition.
bis(2,2'-bipyridyl)copper(II) chloride
To 2,2’-bipyridyl (0.02mol) in acetone-water (50/50),
solution of copper(II) chloride (0.01 mol) in water (25 ml)
was added with stirring. The dark blue solution was concentrated and cooled in an ice bath to produce crystals in quantitative yeild. (m.p. 250C w. decomp.)
bis(2,2'-bipyridyl)copper(II) permanganate
To bis(2,2'-bipyridyl)copper(II) chloride (0.02 mol) in water (25 ml). Potassium permanganate (0.01 mol) in water was added with stirring. The dark purple solution was cooled
and the crystalline compound was collected and dried in air,(yield 95%; m.p.105-110c decomp.)
General procedure for the conversion of hydroxy compounds to their carbonyl compounds.
To the alcohol (0.01mol) in dry CH2Cl2 (50ml) in rbf equipped with a condenser and a mag. stirrer, oxidizing reagent (0.005-0.015mol) was added and stirred 0.25 to 3 hours at room temp. The rxn mix is filtered and solid material washed w. CH2Cl2. Filtrates are combined and evaped. Residue is chromatographed on silica gel, evap. of solvent affords carbonyl compound in 75-100% yeild.
General procedure for the oxidation of benzylic double bonds.
To the alcohol (0.01mol) in dry acetone (25ml) in rbf (50ml) equipped with a condenser and a mag. stirrer, oxidizing reagent (0.01mol) was added and stirred for 10 min. The rxn mix is filtered and solid material washed w. acetone. Filtrates are combined and evaped. Residue is chromatographed on silica gel, evap. of solvent affords carbonyl compound in 80-95% yeild.
Table 1:Oxidation of various organic compounds with BBCP
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Benzyl Alcohol to Benzaldehyde; Time(hr) 0.25; yeild 95%; Oxidant/Reactant 0.5
Benzyl Alcohol to Benzaldehyde(a); Time(hr) 4; yeild 20-30%; Oxidant/Reactant 0.5
Benzhydol to Benzophenone; Time(hr) 0.5; yeild 100%; Oxidant/Reactant 0.5
Furfuril Alcohol to Furfural; Time(hr) 0.3; yeild 90%; Oxidant/Reactant 0.5
9-Phenanthrene-methanol to 9-phenanthrene-carboxaldehyde; Time(hr) 0.9; yeild 95%; Oxidant/Reactant 0.5
Citronellol to Citronellal; Time(hr) 1; yeild 75-83%; Oxidant/Reactant 0.75
Cinnamyl Alcohol to Cinnamaldehyde; Time(hr) 1; yeild 95%; Oxidant/Reactant 1.5
Cinnamyl Alcohol to Benzaldehyde(a); Time(hr) 0.5; yeild 80%; Oxidant/Reactant 1.5
Cinnamyl Alcohol to Benzaldehyde(b); Time(hr) 0.5; yeild 90%; Oxidant/Reactant 1.5
Furfuril Alcohol to Furfural(b); Time(hr) 0.1; yeild 100%; Oxidant/Reactant 0.5
Mandelic Acid to Benzaldehyde(b); Time(hr) 0.5; yeild 90%; Oxidant/Reactant 0.5
p-Nitrobenzyl alcohol to p-nitrobenzaldehyde; Time(hr) 1.5; yeild 90-100%; Oxidant/Reactant 0.75
Hydroquinone to Benzoquinone; Time(hr) 0.25; yeild 100%; Oxidant/Reactant 0.5
Piperonol to Piperonal; Time(hr) 0.5; yeild 100%; Oxidant/Reactant 0.5
C6H5CHCHC(O)C6H5 to Benzaldehyde(b); Time(hr) 0.25; yeild 85-90%; Oxidant/Reactant 1
C6H5CHCHC(O)CH3 to Benzaldehyde(b); Time(hr) 0.25; yeild 80-90%; Oxidant/Reactant 1
C6H5CHCHC(O)H to Benzaldehyde(b); Time(hr) 0.1; yeild 80-85%; Oxidant/Reactant 1
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(a) Reactions performed in water
(b) Reactions in acetone
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