Frans-Cinnamaldehyde

Active Figure 13.19 The 1H NMR spectrum of frans-cinnamaldehyde. The signal of the proton at C2 (blue) is split into four peaks—a doublet of doublets—-by the two nonequivalent neighboring protons. Sign in arwww.thomsonedu.com to see a simulation based on this figure and to take a short quiz. 

Beller and coworkers reported hydrosilylation reactions of organic carbonyl compounds such as ketones and aldehydes catalyzed by Fe(OAc)2 with phosphorus ligands (Scheme 21). In case of aldehydes as starting materials, the Fe(OAc)2/PCy3 with polymethylhydrosiloxane (PMHS) as an H-Si compound produced the corresponding primary alcohols in good to excellent yields under mild conditions [67]. Use of other phosphorus ligands, for instance, PPhs, bis(diphenylphosphino) methane (dppm), and bis(diphenylphosphino)ethane (dppe) decreased the catalytic activity. It should be noted that frans-cinnamaldehyde was converted into the desired alcohol exclusively and 1,4-reduction products were not observed. 

Thermolysis of 12 with frans-cinnamaldehyde afforded the insertion compound 19, formed through the di-insertion of two carbonyl ligands into the C—Si bond of 12. The reaction of 12 with fumaronitrile yielded the cyclization product 20. X-ray study revealed 20 to be a cyclization product which contains two types of disilyl moieties, imino and N,N-bis(silyl)amino, which are connected by a five-membered ring. 

Reaction of stabilized telluronium ylide with aldehydes. Method A - using telluronium ylide (typical procedure).A solution of carbethoxymethyldibutyltelluronium bromide (1.23 g, 3 mmol) in dry THF (3 mL) is added dropwise to a solution of KOf-Bu (0.337 g, 3 mmol) in THF (4 mL) at -20°C. After a few minutes, fran -cinnamaldehyde (0.264 g, 2 mmol) is added over 1 min. The reaction mixture is then stirred for 1 h at -20°C. After the usual work-up, the product is purified by Si02 column chromatography, to give ethyl 5-phenylpenta-(2 , 4 )-dienoate (0.291 g (72%)). GC and NMR of the product reveals a purity of 98%. 

Yet another complication in NMR spectroscopy arises when a signal is split by two or more nonequivalent kinds of protons, as is the case with frans-cinnamaldehyde, isolated from oil of cinnamon (Figure 13,22). Although the n + 1 rule correctly predicts splitting caused by equivalent protons, splittings caused by nonequivalent protons are more complex. 

Pb-tetraacetate added portionwise with ice-cooling during 0.5 hr. to a soln. of frans-cinnamaldehyde in dry benzene through which a stream of NHg-gas is passed, and stirring continued 3 hrs. fran -cinnamonitrile. Y 89%.—This simple and convenient method can be used for the prepn. of a great variety of nitriles. F. e. s. K. N. Parameswaran and O. M. Friedman, Ghem. Ind. 1965, 988. 

To understand the NMR spectI lm of frans-cinnamaldehyde, we have to isolate the different parts and look at the signal of each proton individually. 

In addition to the enamine 369 described in Scheme 2.69, the other four enamines 372-375 obtained from nitroanilines 359 and diphenylacetaldehyde 253o, cyclohexanecarboxaldehyde 253p, fran -cinnamaldehyde 253q, and 1,3-cyclohexanedione 376 were examined (Scheme 2.70) (Wallace et al. 2008). The condensation of aldehydes 253o-q and 1,3-cyclohexanedione 376 with nitroanilines 359 resulted in enamines 372-375 in 91, 88, 85, and 70 % isolated yields, respectively. The A-heteroannulation of 372-375 similarly gave the quinoxaline derivatives 377, 378, 379, 380, 382 in 69, 70, 13, 25, and 26 % isolated yields. In addition to fully aromatic quinoxaline 195, the corresponding A-oxide 381 was obtained, albeit in lower yields in the case of mono-phenyl substituted enamine 374. 

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