The Use of Dimethylformamide as a Formylation Reagent¹

Abstract

NOTES 989The following points about the chemical work are worthy of comment. 1. The addition of a small amount of acetic acid facilitated the reaction of thiosemicarbazide with the carbonyl compounds; so that it was essentially complete in one-half to one hour. Anderson, et aLI4 reported the reaction time to vary from 8 to 80 hours when no acetic acid was added. 2. The synthesis of 5-chloro-2-thenaldehyde in 50-55% yield by formylation of thiophene with N-methylformanilide was recently reported.1° It was therefore interesting to carry out the synthesis of this compound by the Sommelet procedure, in order to compare the yields by the two methods. When 5-chloro-2-methylthiophene was converted to the thenyl bromide with N-bromosuccinimide, and thence to the aldehyde, a 33y0 yield was obtained. When 2-chlorothiophene was chloromethylated by the procedure of Cairns and McKusick" and the thenyl chloride converted to the aldehyde, a 25% yield was obtained. Thus neither process is as efficient as the formylation procedure. lo Experimental Thiosemicarbaz0nes.-The general procedure for the preparation of all the thiosemicarbazones was as follows: 0.1 mole of the carbonyl compound was dissolved in 100 ml. of 50% ethanol (95% ethanol was used for the less soluble compounds) and approximately 2 ml. of glacial acetic acid and 9.1 g. (0.10 mole) of thiosemicarbazide added. The solution was warmed with occasional swirling until the thiosemicarbazide dissolved and then refluxed for approximately one hour. After cooling, the crystalline thiosemicarbazone was collected and recrystallized from 50% ethanol or methanol. The crude yields ranged from 90-96%. The thiosemicarbazones are all 'yellow crystalline compounds, but occasionally on fresh crystallization, some of them appear almost white. After drying and exposure to air, however, they assume a yellow tinge.Intermediate Carbonyl Compounds.-Although all of the thenaldehydes and acetothienones have been previously reported, some of them were prepared by methods not previously applied to these compounds and these are briefly described. 3-Thenaldehyde was prepared by the Sommelet procedure, as previously described.l2 as were 2-chloro-, 2bromo-, and 2,5-dichlor0-3-thenaldehyde.l* In the latter case, 54 g. (59%) of crude 2,5-dichloro-3-thenaldehyde was obtained from 108 g. (0.65 mole) of 2,5-dichloro-3-methylthiophene and 0.6 mole of N-bromosuccinimide, which is a considerable improvement over the yield previously reported, although no changes were made in the procedure. 5-Nitro-2-thenaldehyde was prepared by the method of Patrick and Emerson.14 The observation of Dullaghan, et aZ.,16 that this compound could not be obtained by application of the Sommelet procedure to the product obtained on treatment of 5-nitro-2-methylthiophene with N-bromosuccinimide was confirmed.5-Methyl-, 3-methyl-, 5-t-butyl-and 5-acetamido-2thenaldehyde were obtained by the dimethylformamide formylation procedure described by Campaigne and Archer .I6 The various 2-acetothienones were samples previously prepared ...

Synthesis and Optoelectronic Characterization of Some Star-Shaped Oligomers with Benzene and Triphenylamine Cores

“…4-(N,N-Dimethylamino)benzyl(triphenyl)phosphonium iodine was synthesized according to the reported procedure [30]. 9-Anthrymethyl triphenylphosphonium chloride was synthesized starting from anthracene by three steps: formylation [31], followed by reduction to 9-anthrylmethanol [32], exchange the –OH with chlorine using SOCl 2 as reagent [31], and finally, reaction with PPh 3 [29]. …”

Fluorescent probes for asymmetric lipid bilayers: Synthesis and properties in phosphatidyl choline liposomes and erythrocyte membranes

“…9-Anthraldehyde was synthesized from anthracene using the Vilsmeier reaction as previously described (Campaigne & Archer, 1953). The aldehyde was reduced in methanol with sodium borohydride to 9-hydroxymethyl anthracene (Stewart, 1960).…”

Bacteriorhodopsin analogue from anthryl chromophores

“…The bR analogue (15) An ethanolic solution of anthryl retinal analogue 1 2 was incubated with freshly prepared bOP at ambient temperature in the dark over a period of 24 h. The final ethanol concentration was S 1 % v/v. The growth of the pigment was followed by periodic recording of the absorption spectrum of the mixture.…”