Synthesis of Chrysantemic Acid. Multistep. (1)
3
In the intermediate organic chemistry laboratory course at the University of Wisconsin, we wish to acquaint the students, predominately chemistry majors, with the strategies and techniques involved in carrying out a multistep synthesis. This paper describes a synthesis of chrysanthemic acid (I), which has been used successfully in our laboratory course. The overall synthetic route is outlined in eqn. (1) and is based on a synthesis originally reported by Martel and Huynh 11) at Roussel-Uclaf. Paul F. Schatz University of Wisconsin Madison, Wisconsin 53706 (111) (Nl I 1 ; : &o, 48% HBr kBr g SO~@N~@ (11 (VI) (W) Synthesis of Chrysanthemic Acid A multistep organic synthesis for undergraduate students There are several aspects of the experiment which make it especially suitable for the intermediate or advanced under- graduate chemistrv student. The student's interest in the "~ exprrimtmt is stimulated by the fact rhvt the s\mth<:tic goal, chrysanthemic mid, cnn beobtained f r m pyrethrin flower%. which are a naturally wcurring, eflcctive, and ecologically dafr insectieidr (2-121. In discussinr rent:ral svnthetic strateries such as synthons(l3), strategic ionds (121, and converGnt and linear syntheses (15), the numerous published syntheses (1, 16-36) of chrysanthemic acid can serve as examples for critical analvsis. Presented at the 173rd National Meeting of the American Chemical Society, Chemical Education Division, New Orleans, Louisiana, March, 1977. Dimethyl formamide dried over molecular sieves is sufficient. The starting materials, 3-methyl-2-butenoic acid (II), and 2-methyl-3-huten-2-01 (III), are readily available and inex- pensive. Moreover, it can be shown that these starting mate- rials can be easily synthesized from acetylene and acetone (eqn. (2)). 1. KOCl & hCOgH (1, Thus all the carbon atoms of chrysanthemic acid can he traced hack to com~ounds containine two or three carbon atoms. and this synthesis is an excellentexample of how a struct&ally complicated natural product can he assembled from very simple starting materials. The synthetic plan is convergent which offers advantages other than just thwarting the "arithmetic demon" of linear synthesis (15~). The first steps of the synthesis review ex- perimental techniques, such as refluxing, distillation, and recrvstallization, ~reviously used in the introductory organic . - lah&atory course. The new, more advanced techniques, such as working under an inert atmosphere and high vacuum dis- tillation, are introduced in the later steps. Also,the convergent scheme allows for error (i.e., poor yield or accidental loss of intermediates) without total disaster, since the starting point of any branch of the synthesis is no more than one or two steps away. Finally, the intermediates and products are compatible Summary of Student Results Reactiond Student Yieldsb Time Required (Hr) 79.81.81.86,88.93 (72 * 14) (111) - (VI) - (VIII) 42,42.53,57.64.66.66, 6 68.74,74,75,79.81.86 (66 * 14) (Vlll) + (V) - (IX) 26.34.35.38.46.51,55 8 57.58.58.71.72.77 (52* 16)= (Ix) - (1) 10,33.43.47,49.59.59. 8 62,69.70,79,87,90 (58 * 22) The numbers comespodto cCmpovnds in sqn. (1). Percent of thewetical yield, me numbers in parenmesessremeaverage ad sfadard deviation sad on teal yield of cyclopropanatedprodunn. 468 / Journal of Chemical Education
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Transcript of Synthesis of Chrysantemic Acid. Multistep. (1)
In the intermediate organic chemistry laboratory course at the University of Wisconsin, we wish to acquaint the students, predominately chemistry majors, with the strategies and techniques involved in carrying out a multistep synthesis. This paper describes a synthesis of chrysanthemic acid (I), which has been used successfully in our laboratory course. The overall synthetic route is outlined in eqn. (1) and is based on a synthesis originally reported by Martel and Huynh 11) a t Roussel-Uclaf.
Paul F. Schatz University of Wisconsin
Madison, Wisconsin 53706
(111) ( N l
I 1;: &o, 48% HBr
kBr g S O ~ @ N ~ @
(11 (VI) (W)
Synthesis of Chrysanthemic Acid A multistep organic synthesis for undergraduate students
There are several aspects of the experiment which make it especially suitable for the intermediate or advanced under- graduate chemistrv student. The student's interest in the "~ ~
exprrimtmt is stimulated b y the fact rhvt the s\mth<:tic goal, chrysanthemic mid, cnn beobtained f r m pyrethrin flower%. which are a naturally wcurring, eflcctive, and ecologically dafr insectieidr (2-121. In discussinr rent:ral svnthetic strateries such as synthons(l3), strategic ionds (121, and converGnt and linear syntheses (15), the numerous published syntheses (1, 16-36) of chrysanthemic acid can serve as examples for critical analvsis.
Presented at the 173rd National Meeting of the American Chemical Society, Chemical Education Division, New Orleans, Louisiana, March, 1977.
Dimethyl formamide dried over molecular sieves is sufficient.
The starting materials, 3-methyl-2-butenoic acid (II), and 2-methyl-3-huten-2-01 (III), are readily available and inex- pensive. Moreover, it can be shown that these starting mate- rials can be easily synthesized from acetylene and acetone (eqn. (2)).
1. KOCl & hCOgH (1,
Thus all the carbon atoms of chrysanthemic acid can he traced hack to com~ounds containine two or three carbon atoms. and this synthesis is an excellentexample of how a struct&ally complicated natural product can he assembled from very simple starting materials.
The synthetic plan is convergent which offers advantages other than just thwarting the "arithmetic demon" of linear synthesis (15~) . The first steps of the synthesis review ex- perimental techniques, such as refluxing, distillation, and recrvstallization, ~reviously used in the introductory organic . - lah&atory course. The new, more advanced techniques, such as working under an inert atmosphere and high vacuum dis- tillation, are introduced in the later steps. Also,the convergent scheme allows for error (i.e., poor yield or accidental loss of intermediates) without total disaster, since the starting point of any branch of the synthesis is no more than one or two steps away. Finally, the intermediates and products are compatible
Summary of Student Results
Reactiond Student Yieldsb Time Required (Hr)
79.81.81.86,88.93 (72 * 14)
(111) - (VI) - (VIII) 42,42.53,57.64.66.66, 6 68.74,74,75,79.81.86
(66 * 14) (Vlll) + (V) - (IX) 26.34.35.38.46.51,55 8
57.58.58.71.72.77 (52* 16)=
(Ix) - (1) 10,33.43.47,49.59.59. 8 62,69.70,79,87,90
(58 * 22)
T h e numbers comespodto cCmpovnds in sqn. (1). Percent of thewetical yield, me numbers in parenmesessremeaverage a d sfadard
deviation s a d on teal yield of cyclopropanated produnn.
468 / Journal of Chemical Education
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