Synthesis of cis-jasmone and other cis-rethrones

Abstract

Convenient three-stage syntheses (32-35% overall) of cis-jasmone and cis-cinerone, from readily available 3-(5-methyl-2-furyl)propionaldehyde (2) are described. Wittig reactions, under ' salt-free ' conditions are used for the cis-alkenylation (ca. 12% trans is concurrently produced). Use of an ally1 Wittig reagent (3c) led to a mixture ( 2 : 3) of cis-and trans-dienes which was converted into a mixture of cis-and trans-pyrethrone, from which cis-pyrethrone was separated and characterised. Thermal rearrangement of cis-pyrethrone gave isopyrethrone.Gk-JASBIONE (6b), an odorous principle of jasmine with jasrnololone (7b), are the alcohol components of the flowers, is useful in the reproduction of jasmine fragrance. insecticidal esters of Chrysapttlzemz-lm c i ~i e r a r i a e f o l k ~z . ~ Syntheses have been describedJ1*2 but involve several There is current interest in conversion of ketones of this siages, and proceed in low overall yields ; an exception is a recent synthesis due to Buchi and W i i e ~t . ~ Cinerone (6a) and pyrethrone (6c) are degradation products of cinerolone (7a) and pyrethrolone (7cj respectively, which,

Formation of an unusual dihydropyrazine di-N-oxide during hydrolysis of an .alpha.-oximino acetal

“…(1) known phenylglyoxal 2-oxime 2. The conversion of the known2,3 phenylglyoxal acetal to a mixture of the Z and E isomers of 1 was accomplished in 93% yield by the conditions shown in eq l. 4 The next step, the acid hydrolysis of an -oximino acetal to the corresponding -oximinoaldehyde (eq 2), is at face value a simple…”

“…The formation of 4 from 1 appeared to be a major stumbling block in our synthesis of 2. However, upon examining the change in the 100-MHz nmr spectrum (DMSO-de) of 4 with time, it was seen that the complex pattern characteristic of the protons of 4 slowly disappeared, to be replaced by the three-line spectra one would expect for 2. The half-life of this conversion, as measured by nmr integration, was found to be 110 min at 40°.…”

“…Figure 1.-100-MHz nmr spectrum ( 0-5.5, DMSO-áe) of 2,5-dihydroxy-3,6-diphenyl-5,6-dihydropyrazine 1,4-dioxide(4). Upper curve offset, 400 Hz.…”

Palladium-Catalyzed Hydrophosphorylation of Allenes Leading to Regio- and Stereoselective Formation of Allylphosphonates

“…2 The olefinic bonds formed using the ylides derived from (E)allylic phosphonium salts are usually mixtures of E and Z configurations. 3 Another drawback of the use of allylic ylides lies in the possible loss of the configurational integrity of the olefinic functionality in the allylic moiety. 4 In contrast, the use of (E)-allylphosphonates generally allows better stereochemical control over the geometry of the olefinic bond generated.…”

“…An advantage of allylphosphonates in the olefination over the corresponding phosphonium salts is exemplified by their stereoselectivity and stereospecificity observed in the reactions . The olefinic bonds formed using the ylides derived from ( E )-allylic phosphonium salts are usually mixtures of E and Z configurations . Another drawback of the use of allylic ylides lies in the possible loss of the configurational integrity of the olefinic functionality in the allylic moiety .…”