Cinnamaldehyde complexes

Cinnamaldehyde complexes with iron, 12 246 Circular dichroism flavocytochrome b, 36 271 magnetic, see Magnetic circular dichroism Rieske and Rieske-type proteins, 47 113, 115-116... 

Surprisingly, ATPH can also protect carbonyl carbon of a,P-enals. For example, the reaction of ATPH-cinnamaldehyde complex and butyl Grignard reagent at — 78°C gave a mixture of 1,4-adduct and 1,2-adduct in a ratio of 90 10 (Scheme 6.82), while it is well known that free aldehydes exclusively provide 1,2-addition product [lOlbj. 

For example, although the reaction of ATPH-cinnamaldehyde complex and BuLi gave alkylation products as a 1 1 mixture of 1,4-adduct and 1,2-adduct, the use of aluminum tris[2,6-bis(4-fluorophenyl)phenoxide] (p-F-ATPH) resulted in dramatic improvement of 1,4-selectivity (Scheme 6.84). These results were explained by the high affinity between fluorine atom and lithium atom, thus, the coordination of fluorine atoms on p-F-ATPH to BuLi dominated this highly y-selective butyl transfer reaction (Scheme 6.4). 

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. 

CHROMIUM TRIOXIDE-PYRIDINE COMPLEX, preparation in situ, 55, 84 Chrysene, 58,15, 16 fzans-Cinnamaldehyde, 57, 85 Cinnamaldehyde dimethylacetal, 57, 84 Cinnamyl alcohol, 56,105 58, 9 2-Cinnamylthio-2-thiazoline, 56, 82 Citric acid, 58,43 Citronellal, 58, 107, 112 Cleavage of methyl ethers with iodotri-methylsilane, 59, 35 Cobalt(II) acetylacetonate, 57, 13 Conjugate addition of aryl aldehydes, 59, 53 Copper (I) bromide, 58, 52, 54, 56 59,123 COPPER CATALYZED ARYLATION OF /3-DlCARBONYL COMPOUNDS, 58, 52 Copper (I) chloride, 57, 34 Copper (II) chloride, 56, 10 Copper(I) iodide, 55, 105, 123, 124 Copper(I) oxide, 59, 206 Copper(ll) oxide, 56, 10 Copper salts of carboxylic acids, 59, 127 Copper(l) thiophenoxide, 55, 123 59, 210 Copper(l) trifluoromethanesulfonate, 59, 202... 

In some ca.ses the use of a two-phase system may allow a change in the selectivity. Thus, Joo et al. (1998) have shown that water-soluble Ru hydrides (sulphanatophenylphosphine Ru complexes) give different products in the hydrogenation of cinnamaldehyde with variation in the pH of the aqueous media. At a pH greater than 7.2, cinnamyl alcohol is formed and at a pH less than 5 saturated aldehyde is formed. 

Quinone methides play an important role in lignification. They are produced directly, as intermediates, when lignin monomers, be they hydroxycinnamyl alcohols, hydroxy-cinnamaldehydes, or hydroxycinnamates, couple or cross-couple at their 8- positions. A variety of postcoupling quinone methide rearomatization reactions leads to an array of structures in the complex lignin polymer (Fig. 12.2). 

The disilanickela complex 21 was also found to be a good catalyst for the dehydrogenative double silylation of aldehydes. The nickel-catalyzed reactions of 1,2-bis(dimethylsilyl)carborane 11 with aldehydes such as isobutyraldehyde, trimethylacetaldehyde, hexanal, and benzaldehyde afforded 5,6-carboranylene-2-oxa-l,4-disilacyclohexane.32 34 36 The dehydrogenative 1,4-double silylation of methacrolein and tram-4-phenyl-3-buten-2-one in the presence of a catalytic amount ofNi(PEt3)4 also took place under similar conditions. In contrast, the reaction of 11 with a-methyl-tran.s-cinnamaldehyde and irans-cinnamaldehyde under... 

Panja S, Chakravorti S (2002) Photophysics of 4-(N, N-dimethylamino)cinnamaldehyde/ alpha-cyclodextrin inclusion complex. Spectrochim Acta A Mol Biomol Spectrosc 58(1) 113-122... 

The second Had synthesis provided a route to 2,3,4-trisubstituted pyrroles <06CC2271>. Mixing cinnamaldehyde 27 with aminocarbene complex 28 in the presence of molecular sieves (MS) gave pyrrole 29. The authors proposed a mechanism that included a cyclopropane intermediate and subsequent fragmentation and intramolecular condensation. 

The selectivities in forming cinnamyl alcohol from cinnamaldehyde using these catalysts were poor, and generally resulted in the formation of the saturated aldehyde. This could be overcome by the use of a large excess of phosphine, though at the expense of yield. The same group have demonstrated that ruthenium analogues of the BDNA complex are more active and selective [7]. 

It has been shown previously how water-soluble rhodium Rh-TPPTS catalysts allow for efficient aldehyde reduction, although chemoselectivity favors the olefmic bond in the case of unsaturated aldehydes [17]. The analogous ruthenium complex shows selectivity towards the unsaturated alcohol in the case of crotonaldehyde and cinnamaldehyde [31]. 

Aqueous two-phase hydrogenations are dominated by platinum group metal catalysts containing water-soluble tertiary phosphine ligands. The extremely stable and versatile N-heterocyclic carbene complexes attracted only limited interest, despite the fact that such complexes were described in the literature [62-65]. Recently, it was reported that the water-soluble [RuXY(l-butyl-3-methylimi-dazol-2-ylidene) ( 76-p-cymene)]n+ (X=Ch, H20 Y = C1-, H20, pta) complexes preferentially hydrogenated cinnamaldehyde and benzylideneacetone at the C = C double bond (Scheme 38.5) with TOF values of 30 to 60 h 1 in water substrate biphasic mixtures (80 °C, lObar H2) [66]. 

In 1998, Carreira reported that a catalyst formed from Tol-BINAP, Cu(OTf)2, and 2 equiv of Bu4N+ Ph3SiF2 (TBAT), a soluble fluoride source, was extremely effective in mediating the aldol reaction between a silyldienolate and aromatic or vinyl aldehydes (254). Although initially formulated as a Cu(II) catalyst, subsequent evidence has shown that the active catalyst is a Cu(I) phosphine complex. By using only 2 mol% of the complex, excellent yields and enantioselectivities are observed with a range of aromatic aldehydes (93-95% ee, 86-98% yield), along with some enals (cinnamaldehyde provided the aldol adduct in 83% yield and 85% ee), Eq. 221. 

Benzaldehyde reacts with the diene 28 in the presence of 20 mol% of the chiral boric acids 30 (R = n-Bu, Ph or 2-MeOCgH4), obtained from alkylboric acids and the appropriate derivatives of tartaric acid, at —78 °C for 4-9 h to afford the cis-products 29 in 56-95% yields and 87-97% ee19,20. Benzaldehyde, cinnamaldehyde and various aliphatic aldehydes (n-hexanal, n-heptanal etc) add directly to Danishefsky s diene 4 in ether at —30 °C in the presence of the (R,R)-salen chromium complexes 31 (X = Cl, N3, F or BF4) and 4 A molecular sieves to afford the cycloadducts 32 (e.g. R = Ph, PhCH=CH) in 70-93% ee21. 

Benzylideneacetone reacts with lithiated phenylacetonitrile under kinetic control, in THF and media that favour association, to give 1,2- and 1,4-adducts in proportions which are directly related to concentrations of monomeric and dimeric ion pair species, respectively." An attempt has been made to explain the different regioselec-tivities towards a,-unsaturated carbonyl compounds, including cyclic a-enones and cinnamaldehyde, in terms of intermediate complex formation. 

It is also seen from Table 3.8, that with the various Ru-phosphine complexes as catalysts allowing high conversions of cinnamaldehyde at 35-120 °C under 20-30 bar H2, in many cases water/toluene or water/benzene mixtures were used as solvent Here the interesting point is in that in the absence of excess phosphine, arenes react the following way ... 

It is to be mentioned that water-soluble phosphine complexes of rhodium(I), such as [RhCl(TPPMS)3], [RhCl(TPPTS)3], [RhCl(PTA)3], either preformed, or prepared in situ, catalyze the hydrogenation of unsaturated aldehydes at the C=C bond [187, 204, 205]. As an example, at 80 °C and 20 bar H2, in 0.3-3 h cinnamaldehyde and crotonaldehyde were hydrogenated to the corresponding saturated aldehydes with 93 % and 90 % conversion, accompanied with 95.7 % and 95 % selectivity, respectively. Using a water/toluene mixture as reaction medium allowed recycling of the catalyst in the aqueous phase with no loss of activity. 

---