Stereoselective Syntheses of the Isomeric 5, 10‐Pentadecadienals

Abstract

SummaryThe four isomeric 5,lO-pentadecadienals 1, 2 , 3 and 4 were prepared by stereoselective routes from acetylenic precursors. Two of them, 2 and 4, were also made by Wittig reaction from 2-hydroxytetrahydropyran (29). 2-Hydroxytetrahydropyran (29) yields (Zj-5-alkenols efficiently by Wittig reaction, and (2)-4-hexenol was similarly made from 2-hydroxytetrahydrofuran (66).Efficient methods for the regio-and stereoselective construction of unsaturated aliphatic compounds are highly desirable since a large number of insect pheromones as well as flavouring and perfume chemicals have been found which belong to this group.-\ CHO

Applications of the stereochemically-controlled Horner-Wittig reaction: synthesis of feniculin, (E)-non-6-en-1-ol, a pheromone of the mediterranean fruit fly, (E)- and (Z)-dec-5-en-1-ol, tri-substituted alkenes, and (Z)-α-bisabolene

“…6-Diphenylphosphinoyl-1-hydro.uydecan-5-one (15).-Butyllithium (20.1 ml of a 1 . 5 ~ solution in hexane), pentyldiphenylphosphine oxide (8.16 g, 30 mmol) in dry THF (90 ml) under nitrogen at 0 "C, and 6-valerolactone (3.0 g, 30 mmol) gave the hydroxy ketone (15) (9.63 g, 86.3%) as needles (from EtOAchexane), m.p.…”

“…With TMEDA (1 equiv. ), the same alkylation gave, after flash chromatography (eluting with EtOAc then acetone), 1,l -dimethyl-3-phenylpropyl)diphenylphosphine oxide (530 mg, 15 Method C. Butyl-lithium (7.25 ml, 1 . 5 ~ in hexane) was added dropwise from a syringe to a stirred solution of ethyldiphenylphosphine oxide (5.0 g, 21.73 mmol) and TMEDA (2.5 g, 21.73 mmol) in dry T H F (40 ml) at 0 "C. After 30 min, l-bromo-2phenylethane (2.0 g, 10.86 mmol) was added slowly to the dark red solution; this caused immediate precipitation of a solid.…”

“…Elimination of Ph2P02gave (E)-feniculin (10) showing v, , , . 960 cm-' (out-of-plane deformation for E-CH=CH) and J H H 15 Hz across the double bond (Scheme 2). The stereoselectivity resembles that found with other alkoxy-aryl ketones.…”

“…The Wittig reaction between pentyl triphenylphosphonium bromide and 2H-hydroxytetrahydropyran is 93% Z-selective,' ',' although Schlosser's modification l o would no doubt be E-selective. Either ketone, (15) or (18), for the Horner-Wittig route could be used in this case as the two side-chains are roughly equal in size, but we preferred the ketone (15) as it can be made by acylation with a lactone and there is some evidence" for low stereoselectivity with functional groups in the upper side chain [R' in (2)]. The stereoselectivity of reduction of the ketone (15) was less (75: 25) than that of ketone (12) (85: 15) but threo- (16) was still isolated in 68% yield.…”

Synthesis of the Sex Attractant (7Z,11Z)‐Hexadecadienal of the Citrus Leafminer Moth, Phyliocnietis Citrella Stainton

“…The residue was diluted with dicbloromethane (5 mL) and the mixture was fdtered; the filtrate was collected and evaporated. The residue was purified by column chromatography on silica gel with etherlhexane = 1:2 as the eluant to give the pure Synthesis of (7Z,UZ)-HexadecadienaJ product 8 5 (14), 96 (35),81 (72), 55 (100). The IR and lH NMR spectra were consistent with published data.'…”