Synthesis of (9E,11Z)-Hexadeca-9,11-dienal, Sex Pheromone of the Pecan Nut Casebearer, Acrobasis nuxvorella (Neunzig)

Abstract

The pecan nut casebearer, Acrobasis nuxvorella (Neunzig), is a significant pest of the pecan nut industry. Two alternative syntheses of (9E,11Z)-hexadeca-9,11-dienal, the sex pheromone of the pecan nut casebearer, are described. The key transformation in each sequence is an orthoester Claisen rearrangement.

Key Words

(9E,11Z)-hexadeca-9,11-dienal - conjugated diene - Claisen rearrangement - pheromone - pecan nut casebearer - Acrobasis nuxvorella

References

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2

Knutson, A.; Ree, B. Controlling the Pecan Nut Casebearer http//entowww.tamu.edu/extension/bulletins/l-5134.html 1998.

9

The α,ω-bromoheptyl THP ether needed for the coupling reaction was prepared from 1,7-heptanediol by monobromination with 48% HBr [19] followed by protection with 3,4-dihydro-2H-pyran, catalyzed by HCl, [20] in an overall yield of 83%. The coupling reagent was generated using magnesium powder [21] in THF at room temperature and then added to a CuI suspension at -78 °C to form the corresponding coupling reagent.

14

Monobromination with HBr [19] and protection with 3,4-dihydro-2H-pyran [20] afforded the α,ω-bromopentyl THP ether in an overall yield of 50%. NMR analysis of the final product was in accordance with literature data. [22] The Grignard reagent was prepared using magnesium turnings in THF at r.t. and was allowed to stir overnight due to the sluggish nature of the reaction in order to ensure complete formation. The resulting solution was added to a CuI suspension in THF at -78 °C to yield the corresponding coupling reagent.

16

Personal communication from M. A. Muegge and A. E. Knutson, Texas A & M University, Texas Agricultural Extension Service.