Hydroxy-citronellal

SYNS CYCLAUA CYCLOSIA 3.7-DIMETHYL-7-HYDROXYOCTANAL FE L No. 2583 FIXOL HYDROXYCITRONELLAL (FCC) 7-HYDROXY-CITRONELLAL 7-HYDROXY-3,7-DIMETHYL OCTANAL 7-HYDROXY-3,7-DIMETH LOCTAN-l-AL LAURINE ULYL ALDEHYDE MUSUET SYNTHETIC MUSUETTINE PRINCIPLE PHIXIA... 

Snider has shown that thermolysis of 2,6-dimethyl-2,7-octadienal at 350°C yielded three compounds, 365-367, having the iridoid skeleton. The lactone 368 was made by cyclization of the corresponding hydroxy acid ( 8-hydroxy-citronellic acid ), and its tert-butyldimethylsilyl enol ether rearranged in an Ireland-type Claisen rearrangement, yielding the iridoid acid 369 after removal of the silyl group with HF in acetonitrile. The latter was converted (by hydrobora-tion-oxidation) into both isomers of dihydronepetalactone (370) (erroneously considered to be unsynthesized by the authors, who clearly did not read Vol. 4, p. 497). Iridomyrmecin (371) is also accessible from 369 (Scheme 30). 

Since the blossom oil of lily of the valley is not commercially available, the perfumers have to rely on synthetic substitutes, such as hydroxy-citronellal (1), Lilial (3) and Bourgeonal (6) to create their muguet fragrances. The oldest lily of the valley odorants, hydroxycitronellal and cyclamen aldehyde (2) (Winthrop Chem. Corp., 1929), were discovered by chance. Serendipity still continues to play an important role. Anselmi et al. (1992) synthesized and organoleptically screened a series of 38 tetrahydropyranyl ethers. This class of compounds was chosen because of their ease of synthesis and purification, and because of their stability in alkaline media, conditions under which aldehydes tend to undergo aldol condensations. Two compounds (24 and 25) were described as having a white, floral odour reminiscent of hydroxycitro-... 

Figure 15.2 Comparison between the structures of the tetrahydropyranyl ethers of 4-t-butylphenol and c s-4-methylcyclohexanol, and those of hydroxy citronellal and Lilial . The structures have been drawn with similar orientation of the polar group to better visualize similarities in size and shape of the hydrocarbon region...

Aurantiol . [BASF AG] Hydroxy-citronellal/methylanthranilate blend sweet final fiagnnce. 

Use C. find use in perfume and soap industries and for the preparation of menthol, citronellol, hydroxy-citronellal, and isopulegol (see p-menthenols). Dog collars impregnated with C. are purported to calm dogs and induce them to bark less. ... 

Methyl 6-hydroxy-3-methylhexanoate is our 1,6-difunctional target molecule. Obvious precursors are cyclohexene and cyclohexadiene derivatives (section 1.14). Another possible starting material, namely citronellal, originates from the "magic box of readily available natural products (C.G. Overberger, 1967, 1968 E.J. Corey, 1968D R.D. Clark, 1976). 

Biochemisch werden Aldehyde i. a. zu den entsprechenden Alkoholen reduziert, wobei sie gelegentlich der mikrobiologischen Cannizzaro-Disproportionierung zu Carbonsaure und Alkohol unterliegen konnen [z. B. 3,7-Dimethyl-octen-(6)-al (Citronellal) zu 8-Hydroxy -2,6-dimethyl-octen-(2) und 3,7-Dimethyl-octen-(6)-sdure]1. 

Simple transformations (hydrolysis of the pyrophosphate group to a hydroxy group, elimination, oxidation, etc.) convert geranyl pyrophosphate to monoterpenes such as geraniol, myrcene, and citronellal. 

The cationic BINAP-Rh complexes catalyze asymmetric 1,3-hydrogen shifts of certain alkenes. Diethylgeranylamine can be quantitatively isomerized in THF or acetone to citronellal di-ethylenamine in 96-99% ee (eq 17). This process is the key step in the industrial production of (-)-menthol. In the presence of a cationic (R)-BINAP-Rh complex, (5)-4-hydroxy-2-cyclopentenone is isomerized five times faster than the (R) enantiomer, giving a chiral intermediate of prostaglandin synthesis. ... 

L-Menthol, hydroxy-dihydro-citronellal, d-and L-citronellol Isomerization of allyl amine with Rh-binap >1000 t/y Takasago [5-7]... 

Various aromatic aldehydes react with active methylene compounds in the presence of piperidine to give the corresponding dipiperidines (18), which are in equilibrium with the iminium ion (16) under the reaction conditions (Scheme 8). In addition, the primary reaction products (17) of iminium ions (16) with the active methylene compound (11) can also be isolated. In the reaction of V,iV-dimethylbarbituric acid and citronellal using catalytic amounts of ethylenediammonium diacetate, the 3-hydroxy-1,3-dicarbonyl has been identified by NMR spectroscopy. ... 

Pure citronellal is a colorless liquid with a refreshing odor, reminiscent of balm mint. Upon catalytic hydrogenation, citronellal yields dihydrocitronellal, citronellol, or dihydrocitronellol, depending on the reaction conditions. Protection of the aldehyde group, followed by addition of water to the double bond in the presence of mineral acids or ion-exchange resins results in formation of 3,7-dimethyl-7-hydroxy-octan-l-al (hydroxydihydrocitronellal). Acid-catalyzed cyclization to iso-pulegol is an important step in the synthesis of (-)-menthol. 

The analogous situation for cyclohexyl systems undergoing Type I intramolecular ene reactions is exemplified by the cyclization of (.S )-3,7-dimethyl-6-octenal (citronellal) where mixtures are produced, in accord with expectations based upon the results of the reaction with methyl 3-[( )-3-benzoxy-l-propenyl]-6-oxohexanoate (see Table 5)101-102. However, a chiral zinc-based Lewis acid has been shown to effect this transformation with a high level of selectivity for the hydroxy group tram to the isopropylidene group (vide infra). 

Hydroxy- Cyclamen Lilial Lyral Florosa Bourgeonal citronellal aldehyde... 

By the time comprehensive reviews by Wilds (29) in 1944 and Djerassi (30) in 1953 became available, MPV reactions were a standard reductive technique in the organic chemistry community. For example, a 1945 patent (20) describes the utility of using aluminum alkoxides in the presence of an organic nitrogen as a weak base for the reduction of carbonyl groups on oxo compounds such as 7-hydroxy-cholesterol acetate, benzaldehyde, cinnamic aldehyde, and citronellal. 

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