Cesium Effect: High Chemoselectivity in Direct N-Alkylation of Amines
A novel method for the mono-N-alkylation of primary amines, diamines, and polyamines was developed using cesium bases in order to prepare secondary amines efficiently. A cesium base not only promoted alkylation of primary amines but also suppressed overalkylations of the produced secondary amines. Various amines, alkyl bromides, and alkyl sulfonates were examined, and the results demonstrated this methodology was highly chemoselective to favor mono-N-alkylation over dialkylation.
Reference:
J. Org. Chem. 67, 674-683 (2002) (https://www.thevespiary.org/rhodium/Rhodium/pdf/amine.alkylation.cesium-effect.pdf)
(https://www.thevespiary.org/rhodium/Rhodium/pdf/amine.alkylation.cesium-effect.pdf)
I have understood that the yields were higher with electrolytic iron than ordinary iron powder, but you could also check out this thread: Post 320730 (https://www.thevespiary.org/talk/index.php?topic=11723.msg32073000#msg32073000)
(Barium: "Another easy route to P-2-P´s", Novel Discourse).
I don't think I have ever reccommended boiling 2,4,5-trimethoxyphenyl-2-nitropropene in any acid.
The Fe/AcOH reduction I was talking about is from Pihkal #100 (http://www.erowid.org/library/books_online/pihkal/pihkal109.shtml)
(http://www.erowid.org/library/books_online/pihkal/pihkal109.shtml)
An alternate synthesis of 3,4-methylenedioxyphenylacetone starts originally from piperonal. A suspension of 32 g electrolytic iron in 140 mL glacial acetic acid was gradually warmed on the steam bath. When quite hot but not yet with any white salts apparent, there was added, a bit at a time, a solution of 10.0 g of 1-(3,4-methylenedioxyphenyl)-2-nitropropene in 75 mL acetic acid (see the synthesis of MDA for the preparation of this nitrostyrene intermediate from piperonal and nitroethane). This addition was conducted at a rate that permitted a vigorous reaction free from excessive frothing. The orange color of the reaction mixture became very reddish with the formation of white salts and a dark crust. After the addition was complete, the heating was continued for an additional 1.5 h during which time the body of the reaction mixture became quite white with the product appeared as a black oil climbing the sides of the beaker. This mixture was added to 2 L H2O, extracted with 3x100 mL CH2Cl2, and the pooled extracts washed with several portions of dilute NaOH. After the removal of the solvent under vacuum, the residue was distilled at reduced pressure (see above) to provide 8.0 g of 3,4-methylenedioxyphenylacetone as a pale yellow oil.