Of cinnamyl alcohol

Physical and Chemical Properties. Although both the (E)- and (Z) [4510-34-3] isomers of cinnamyl alcohol are known in nature, (E)-cinnamyl alcohol [4407-36-7] is the only isomer with commercial importance. Its properties are summari2ed in Table 4. 

When heated in the presence of a carboxyHc acid, cinnamyl alcohol is converted to the corresponding ester. Oxidation to cinnamaldehyde is readily accompHshed under Oppenauer conditions with furfural as a hydrogen acceptor in the presence of aluminum isopropoxide (44). Cinnamic acid is produced directly with strong oxidants such as chromic acid and nickel peroxide. The use of t-butyl hydroperoxide with vanadium pentoxide catalysis offers a selective method for epoxidation of the olefinic double bond of cinnamyl alcohol (45). 

One of the first practical methods for the manufacture of cinnamyl alcohol involved reduction of cinnamic aldehyde diacetate with iron filings in acetic acid. This approach suffered from low yields and Hberation of a significant amount of the starting aldehyde. 

The commercial production of cinnamyl alcohol is accompHshed exclusively by the reduction of cinnamaldehyde. 

Uses. Cinnamyl alcohol and its esters, especially cinnamyl acetate, are widely employed in perfumery because of their excellent sensory and fixative properties. They are frequently used in blossom compositions such as lilac, jasmine, lily of the valley, hyacinth, and gardenia to impart balsamic and oriental notes to the fragrance. In addition, they ate utilized as modifiers in berry, nut, and spice flavor systems. The value of cinnamyl alcohol has also been mentioned in a variety of appHcations which include the production of photosensitive polymers (49), the creation of inks for multicolor printing (50), the formulation of animal repellent compositions (51), and the development of effective insect attractants (52). 

Another point for structural diversification is the sulfonamide group. Imai had already shown that a wide variety of groups could be introduced at this position to optimize the reaction. Since a wide variety of sulfonyl chlorides are commercially available, a number of different types of groups could be examined (Scheme 3.34). Testing of a variety of aryl and alkyl groups on the 1,2-cyclohexanediamine backbone demonstrates that the simple methanesulfonamide 122 is clearly superior or equal to many other analogs in the cyclopropanation of cinnamyl alcohol (Table 3.11). Another concern which was directly addressed by this survey was the question of catalyst solubility. 

Employing protocol V with the methanesulfonamide catalyst 122, a 93 7 er can be obtained in the cyclopropanation of cinnamyl alcohol. This high selectivity translates well into a number of allylic alcohols (Table 3.12) [82]. Di- and tri-substi-tuted alkenes perform well under the conditions of protocol V. However, introduction of substituents on the 2 position leads to a considerable decrease in rate and selectivity (Table 3.12, entry 5). The major failing of this method is its inability to perform selective cyclopropanations of other hydroxyl-containing molecules, most notably homoallylic alcohols. 

Phenyl-propyl alcohol, CgH. CHj. CH.2. CHj. OH, is the next highest homologue of phenyl-ethyl alcohol, and is also known as hydro-cinnamyl alcohol. Like the last described bodies it has been known for many years, its first preparation being described in the Aivnalen (188, 202). It occurs as a cinnamic acid ester in storax, and as an acetic ester in cassia oil. It is prepared synthetically by the reduction of cinnamyl alcohol with sodium amalgam and water, or by the reduction of cinnamic or benzyl acetic esters with sodium and absolute alcohol. It has the following characters —... 

In 1998, Kurt and Halm reported the preparation of resin-based bis(sulfo-namides) ligands in order to extend the precedent methodology to the solid phase. Therefore, the solid-phase catalyst depicted in Scheme 6.21 was found to be able to mediate the Simmons-Smith cyclopropanation of cinnamyl alcohol with an enantioselectivity of 65% ee. 

Other bis(sulfonamides) ligands based on more flexible diamines have been investigated by Denmark et al. as promoters for the enantioselective Simmons-Smith cyclopropanation of cinnamyl alcohol. This study has revealed a... 

Scheme 6.21 Simmons-Smith cyclopropanation of cinnamyl alcohol with resin-based bis(sulfonamides) ligand.

Ros Barcelo, A. Pomar, F. Oxidation of cinnamyl alcohols and aldehydes by a basic peroxidase from lignifying Zinnia elegans hypocotyls. Phytochemistry 2001, 57, 1105-1113. 

Addition of / -toluenesulfonic imidazolide in benzene to a suspension in benzene of sodium cinnamoxide in a 1 2 molar ratio affords the dicinnamyl ether in 71% yield. Apparently, a highly reactive, so far not isolated sulfonate of cinnamyl alcohol is formed first (a), which then reacts further with a second mole of alkoxide to form the ether according to (b) ... 

Of particular interest are oxidations of unsaturated alcohols, for example, oxidation of cinnamyl alcohol to cinnamaldehyde,74,75 and special promoters have been added to increase selectivity (Fig. 6.13).75 Although the functions of these promoters are still not fully undestood, some authors attribute their increased selectivity to physical blocking of reaction sites. This blocking reduces the size of the active site ensemble and suppresses the tendency for alcohols to strongly adsorb and dissociate on Pt.75... 

FIGURE 6.13 Bi promotion of Pt to increase selectivity of cinnamyl alcohol to cinnamaldehyde.75... 

An elegant approach toward formation of the central tetrahydropyrimidine ring has been reported by Tamura and co-workers who utilized an aza-Diels-Alder cyclization of ethyl ( )-3-aza-3-(l,3-benzoxazol-2-yl)propenoate 266 with a range of cinnamyl alcohols 267 catalyzed by l,l,3,3-tetra- -butyl-l,3-diisothiocyanatodistannoxane, and subsequent lactonization to generate the tricyclic core structure 268 (Scheme 18) <1998J(P1)3389>. 

K. I. Kuroda, Pyrolysis trimethylsilylati on analysis of lignin preferential formation of cinnamyl alcohol derivatives, J. Anal. Appl. Pyrol., 56, 79 87 (2000). 

Figure 5-15 shows a possible transition state for the enantioselective cyclopropanation of cinnamyl alcohol in the presence of dioxaborolane 206. This model predictes the absolute configuration of the products. 

A 1-1., three-necked, round-bottomed flask equipped with a Trubore stirrer, a pressure-equalizing dropping funnel, and a reflux condenser with a drying tube is charged with 350 ml. of acetonitrile (Note 1) and 106.4 g. (0.41 mole) of triphenylphos-phine (Note 2). The flask is cooled in an ice-water bath (Note 3), and 64 g. (0.40 mole) of bromine is added dropwise over a period of ca. 15-20 minutes (Notes 4 and 5). The ice-water bath is removed, and a solution of 54 g. (0.40 mole) of cinnamyl alcohol in 50 mi. of acetonitrile is added in portions over a period of 5-10 minutes with continued stirring (Note 6). The solvent is removed by distillation with the use of a water aspirator (30-40 mm.) and an oil bath until the bath temperature reaches 120°. The water aspirator is replaced by a vacuum pump and the water-cooled condenser with an air condenser, and the distillation is continued with rapid stirring (Notes 7, 8, and 9). Most of the product (Note 10) distills at 91-98° (2-4 mm.), and about 59 g. of product crystallizes in the receiving flask (63-75% yield) (Note 11). 

The solution of cinnamyl alcohol (2.68 g in 3mL of dry dichloromethane) was added dropwise over 1 hour via a syringe. 

Figure 14.7. Electronic effects in asymmetric epoxidation of cinnamyl alcohols...

The effect of a surfactant such as do-decylbenzene sulfonate (DBS) has been investigated and the DBS concentration slightly influences the current efficiency [213]. The oxidation of cinnamyl alcohol to cinnamaldehyde with a solid... 

Much more conveniently, even a,)S-unsaturated esters can he transformed into a,)S-unsaturated alcohols by very careful treatment with lithium aluminum hydride [1073], sodium bis(2-methoxyethoxy)aluminum hydride [544] or diiso-butylalane [1151] (Procedure 18, p. 208). An excess of the reducing agent must be avoided. Therefore the inverse technique (addition of the hydride to the ester) is used and the reaction is usually carried out at low temperature. In hydrocarbons as solvents the reduction does not proceed further even at elevated temperatures. Methyl cinnamate was converted to cinnamyl alcohol in 73% yield when an equimolar amount of the ester was added to a suspension of lithium aluminum hydride in benzene and the mixture was heated at 59-60° for 14.5 hours [1073]. Ethyl cinnamate gave 75.5% yield of cinnamyl alcohol on inverse treatment with 1.1 mol of sodium bis(2-methoxy-ethoxy)aluminum hydride at 15-20° for 45 minutes [544]. 

Kabalka and co-workers reported the direct cross-coupling of cinnamyl alcohols with aryl- and vinylboronic acids using simple rhodium salts in an environmentally benign ionic liquid medium (Eq. 6) [30]. The ability to utilize allylic alcohols, without activation, is significant from the viewpoint of atom economy, yet challenging due to the poor leaving group ability of hydroxide. 

Scheme 15 Scope of the Bi(OTf)3-catalyzed alkylation of cinnamyl alcohols and acetates...

In plant cell walls, lignin monomers seem to be present in vivo in the form of cinnamyl alcohols. In vitro, their acid precursors can also be oxidized by peroxidases (3). In order to gain further insight into the possible... 

---