Trans-cinnamaldehydes

Yet another complication in 1H NMR spectroscopy arises when a signal is split by two or more nonequivalent kinds of protons, as is the case with trans-cinnamaldehyde, isolated from oil of cinnamon (Figure 13.19). Although the n + l rule predicts splitting caused by equivalent protons, splittings caused by nonequivalent protons are more complex. 

To understand the 1H NMR spectrum of trans-cinnamaldehyde, we have to isolate the different parts and look at the signal of each proton individually. 

Surfactants greatly improve the performance of trans-cinnamaldehyde as a corrosion inhibitor for steel in HCl [741,1590,1591]. They act by enhancing the adsorption at the surface. Increased solubility or dispersibility of the inhibitor is an incidental effect. N-dodecylpyridinium bromide is effective in this aspect far below its critical micelle concentration, probably as a result of electrostatic adsorption of the monomeric form of N-dodecylpyridinium bromide. This leads to the formation of a hydrophobic monolayer, which attracts the inhibitor. On the other hand, an ethoxylated nonylphenol, a nonionic surfactant, acts by incorporating the inhibitor into micelles, which themselves adsorb on the steel surface and facilitate the adsorption of trans-cinnamaldehyde. 

It has been shown that the corrosion rates of various steels can be reduced to less than 1 mg/cm /hr using ternary inhibitor mixtures containing quaternary ammonium salts, trans-cinnamaldehyde, and potassium iodide in amounts of 0.2% of each component [1758]. 

Mixtures of aldehydes with surfactants are active in preventing corrosion, in particular in the presence of mineral or organic acids [646]. The aldehyde may be trans-cinnamaldehyde. The surfactant may be N-dodecylpyridinium bromide or the reaction product of trimethyl-1-heptanol with ethylene oxide [645]. Such aldehyde and surfactant mixtures provide greater and more reliable corrosion inhibition than the respective compositions containing aldehydes alone. 

The useful chemoselective feature of the reaction is apparent from the reduction of trans-cinnamaldehyde (cinnamaldehyde/NaBH4-alumina, 1 1 mol equivalent) olefmic moiety remains intact and only the aldehyde functionality is reduced in a facile reaction. 

Of many compounds tested, trans-cinnamaldehyde was most effective in delaying the approach to food by coyotes (Jankowsky etal, 1974). Other studies found /3-chloroacetyl chloride, a strong irritant and lachrymator, an effective olfactory repellent, while cinnamaldehyde was somewhat active in delaying approach to a visible food source (Lehner eta/., 1976). 

In this paper we will report on using a series of modifiers to enhance selectivity during 1-phenyl-1-propyne over a Pd/alumina catalyst. The modifiers, trans-cinnamaldehyde, trans-cinnamonitrile, 3-phenylpropionitrile, and 3-phenylpropylamine, were chosen to have a functionality that potentially could adsorb more strongly than an alkene and to be unreactive under the reaction conditions. 

The reaction of 1-phenyl-l-propyne (IPP) was then studied after modilying the catalyst with trans-cinnamaldehyde (TCA), trans-cinnamonitrile (TCN), 3-phenylpropionitrile (3PPN), and 3-phenylpropylamine (3PPA). The first-order rate constant calculated for the loss of 1-phenyl-l-propyne in each of the systems is reported in Table 1. All the modifiers were unreactive under the conditions used. 

During the course of studies on these asymmetric nitroaldol reactions catalyzed by chiral ammonium bifluorides 6 (X= HF2), the reaction of 23a was attempted with trans-cinnamaldehyde, a representative a,P-unsaturated aldehyde, under the influence of (R,R)-6c (X = HF2, 2mol%) in THF at — 78 °C. The starting aldehyde was consumed within 30 min at this temperature and, surprisingly, the 1,4-addition product 25 was obtained predominantly as a diastereomeric mixture with concomitant formation of the initially expected nitroaldol (1,2-addition product) 26 [72% combined yield, 25/26 = 17 1, syn/antiof25 = 85 (4% ee) l 5 (25% ee)] (Scheme 9.13). 

The efficient homogeneous catalysis of chiral ammonium bifluorides of type 15 has been further utilized for achieving an asymmetric Michael addition of silyl nitronates to a,/ -unsaturated aldehydes. Here, chiral ammonium bifluoride 15b bearing a 3,5-di-tert-butylphenyl group was found to be the catalyst of choice, and the reaction of 16a with trans-cinnamaldehyde under the influence of (R,R)- 15b (2 mol%) in THF at —78 °C produced the 1,4-addition product 18 predominantly (18/19 = 24 1) as a diastereomeric mixture (syn/anti = 78 22) with 85% ee of the major syn isomer (Scheme 4.9). Further, use of toluene as solvent led to almost exclusive formation of the 1,4-adduct (18/19 = 32 1) with similar diastereoselec-tivity (syn/anti = 81 19), and critical enhancement of the enantioselectivity was attained (97% ee) [15]. 

The significant synthetic advantage of this approach is the isolation of regio-and stereo-defined enol silyl ethers of optically active y-nitro aldehydes (Table 4.2). For example, after the reaction of 16a with trans-cinnamaldehyde, the resulting mixture can be directly purified by silica gel column chromatography to produce the optically active enol silyl ether 20a in 90% yield (Table 4.2, entry 1). High... 

The boll weevil antifeedants, anthranilic acid, gentisic acid, senecioic acid, trans-cinnamic acid, trans-cinnamaldehyde and camphor have been Isolated from the Peruvian plant Alchornea triplinervia (Euphorbiaceae). Anthranilic acid and camphor also showed significant Inhibition of growth of the tobacco budworm. 

The H NMR spectrum of trans-cinnamaldehyde. The signal of the proton at C2 (blue) is split into four peaks—a doublet of doublets—by the two nonequivalent neighboring protons. 

Oil of cassia, Chinese type - Determination of trans-cinnamaldehyde content - Gas chromatographic method on capillary columns... 

L2FeCHFCF2CF2CHF in 40% yield, notably with the opposite regiochemistry to that observed for Ni above. Similarly, irradiation of Fe(CO)4 (trans-cinnamaldehyde) in... 

The C5-C12 fragment was prepared by reaction of trans-cinnamaldehyde with a boron enolate to afford the corresponding aldol... 

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