Heptanal condensation reactions with

Now the most important Route la will be illustrated by means of the synthesis of BIPHEPHOS (Scheme 2.89) [7]. The required biphenyl phosphorchloridite can be prepared by the reaction of PCI3 with 2,2 -dihydroxybiphenol in the presence of NEtj, as suggested by the Amsterdam group [78]. Alternatively, the reaction can be conducted in a suspension of toluene in the absence of a base, under the condition that HCl is removed under vacuum [79]. The chlorophosphite is used in the second step for the condensation reaction with the substituted biphenol in the presence of pyridine. Final crystallization from acetonitrile produces the desired product. Care should be taken with traces of chlorine or acetonitrile, which affects the longterm stability of the diphosphite [80]. These contaminations can be removed by recrystallization, for example, from o-xylene, n-heptane, or ethyl acetate, or by washing with acetone. 

Several cross-aldol condensations have been performed with alkaline earth metal oxides, including MgO, as a base catalyst. A general limitation of the cross-aldol condensation reactions is the formation of byproducts via the self-condensation of the carbonyl compounds, resulting in low selectivities for the cross-aldol condensation product. For example, the cross-condensation of heptanal with benzalde-hyde, which leads to jasminaldehyde (a-K-amylcinnamaldehyde), with a violet scent... 

The first pyrazolo[l,5-c]pyrimidine derivative (191) was prepared by condensing thiosemicarbazide with heptane-2,4,6-trione in the presence of perhydroacetic acid (72CB388). This reaction was adopted for the preparation of derivatives of 191 (X = O, NH), and later used to synthesize other pyrazolo[ 1,5-c] pyrimidines (71GEP2131790). 

A. Z, s-Vndeoanediona. A 1000-mL, three-necked, round-bottomed flask equipped with a mechanical stirrer, short gas inlet tube, and an efficient reflux condenser fitted with a potassium hydroxide drying tube is charged with 26.8 g (0.1 mol) of 3-benzyl-5-(2-hydroxyethyl)-4-methyl-l,3-thiazolium chloride (Note 1), 500 mL of absolute ethanol, 77.2 g (1.1 mol) of 3-buten-2-one (Note 2), 60.6 g (0.6 mol) of triethylamlne (Note 3), and 114.2 g (1.0 mol) of heptanal (Note 4). A slow stream of nitrogen (Note 5) is started and the mixture is stirred and heated in an oil bath at 80°C. After 16 hr the reaction mixture is cooled to room temperature and concentrated by rotary evaporation. Then 500 mL of chloroform is added to the residue and the... 

Liquid phase aldol condensation reaction between heptanal and benzaldehyde is studied over two series of oxynitride catalysts aluminium phosphate oxynitrides AlPON and mixed aluminium gallium phosphate oxynitrides AlGaPON , with increasing nitrogen contents (0-14 wt.% for AlPON and 0 - 16 wt. % for AlGaPON ). The main products are jasminaldehyde and 2-pentyl-2-nonenal. Jasminaldehyde is formed via the cross-aldol condensation reaction between heptanal and benzaldehyde and 2-pentyl-2-nonenal is formed via the self-condensation reaction of heptanal. 

In the present study, we will desribet the link between the nitridation parameters and the performances of oxynitrides for the synthesis of jasminaldehyde. Jasminaldehyde (a-amylcinnamaldehyde) is obtained through the aldol condensation of heptanal with benzaldehyde, in the liquid phase. It is a fine chemical of commercial interest [2], as it is used by the flavour and perfume industry. On top of its industrial interest, the aldol condensation reaction between heptanal and benzaldehyde is an interesting test reaction to assess the acid-base properties of heterogeneous catalysts. Heptanal is more reactive than... 

Liquid samples were regularly withdrawn with a filtering syringe and analyzed by a gas chromatograph (Perkin Ehner) equipped with an FID detector and using a capillary column (CPSilSCB, 25 m). All the isomers (Z, E) of crosscondensation and self condensation reactions have been separated and identified by H-NMR and GC-MS. Quantitative determinations were based on the measured response factors of the reactants and reaction products. We checked that reactions were carried without transfer limitations. The selectivity for a particular product was defined as the mmol of this product divided by the total mmol of heptanal converted. 

Table 2 presents the catalytic results obtained over Al(Ga)PON samples for the aldol condensation reaction of benzaldehyde with heptanal. It shows that the basic nitrided Al(Ga)PON samples are more selective to jasminaldehyde than the phosphates precursors. A similar effect was already observed for ZrPON (nitrided zirconophosphates) and another series of AlGaPON samples [8]. 

We showed, over two different series of Al(Ga)PON oxynitrides catalysts, that the nitridation of phosphate precursors has a positive effect on the selectivity to jasminaldehyde for the mixed aldol condensation reaction of heptanal with benzaldehyde. The influence of nitridation on the product distribution was interpreted in terms of changes in the relative density of acid and basic sites on the catalyst surface. Decreasing the acidity and increasing the basicity through nitridation enhances the simultaneous activation of benzaldeyde and heptanal and favors the cross condensation reaction between those two aldehydes, rather than the self-condensation of heptanal. 

The same catalyst has been employed in the jasminaldehyde synthesis by condensation of benzaldehydc w ilh heptanal under true batch reactor conditions 25. Ttic target compound was isolated in lower yield (79%) with respect to that obtained by carrying out the reaction with PTBD (99%) but with a considerably higher selectivity (70% vs 49%). In conclusion TBD immobilized on MCM-4I results in a catalyst that is considerably more thermally stable, and shows a better selectivity than PTBD. This is probably an indication for a shape selective reaction in the pore system. The authors also reported the interesting results obtained by testing the MCM-41-TBD in a packed bed micro-reactor (see Table 7). 

The reaction is carried out under argon in a 2-liter three-necked flask fitted with a mechanical stirrer, reflux condenser, 250-ml pressure-equalizing addition funnel, and gas inlet and outlet. After purging with argon, the flask is charged with a solution of 89 g (0.48 mole) of ferrocene in 1 liter of dry tetrahydrofuran. The solution is next heated to 45°, and there is added dropwise with stirring, 155 ml (0.29 mole) of an -butyllithium solution (15% in heptane-pentane, 2 1, Foote Mineral Co.) during a period of 75 minutes. The resultant solution is maintained at 45° for an additional 2 hours, then is cooled to —77° by means of an external Dry Ice-chloroform bath. 

A 50-mL round-bottomed flask equipped with a reflux condenser is charged with a solution of 3-hexyne (4.5 mL, 35.5 mmol) and Me3SiCl 14 (4.5 mL, 34.5 mmol) in 15 mL abs. THF and with 1 g Pd/C (10%). The reaction mixture is heated under reflux for 3 h with exclusion of humidity. Filtration and evaporation in vacuo give 3.3 g (100%) hexaethylbenzene 2165 as a colorless liquid (b.p. 50 °C/ 20 mm) which subsequently solidifies. RecrystaUization from heptane affords colorless needles, m.p. 130°C [78] (Scheme 13.35). 

A more general reaction between kojic acid and aldehydes is a trimolecu-lar condensation discovered by Barham and Reed." By a process of elimination, they arrived at the conclusion that C6 of kojic acid was most probably the point of attack two molecules of kojic acid reacted with one molecule of the aldehyde, with the elimination of one molecule of water, giving a product of structure LXXV. Such compounds were prepared from kojic acid and the following aldehydes the normal alkanals from formaldehyde to heptanal, benzaldehyde, cinnamaldehyde, hydrocinnamaldehyde, 2-furaldehyde, and acrolein. The compound derived from kojic acid and benzaldehyde (LXXV, R = phenyl) was also obtained by treating LXXII (R = phenyl) with hot, aqueous sodium carbonate.92... 

In a subsequent report, however, the thiazolopapains were shown to be competent in catalyzing a carbon-carbon bond-forming reaction of the acetoin condensation type (Fig. 14) [50]. The reaction of the papain derivatives with 6-oxo-heptanal was assayed at neutral pH (Fig. 14). The course of the reaction was monitored by HPLC and the products analyzed by H NMR. In the case of the... 

Recently, cross-aldol condensation of benzaldehyde with n-heptaldehyde to give jasminaldehyde (Scheme 13) has been reported a mesoporous molecular sieve Al-MCM-41 with supported MgO was the catalyst. The reactions were carried out in a stirred autoclave reactor with a molar benzaldehyde/heptanal ratio of 10 at 373-448 K (236). The results show that Al-MCM-41 is catalytically active, and its activity is significantly increased by the deposition of MgO (Table V). Increasing the amount of deposited MgO on Al-MCM-41 decreases the surface area but enhances the catalyst basicity. The basicity is well correlated with the catalytic activity, although the selectivity to jasminaldehyde is not the selectivity is essentially independent of temperature, pressure, time of the reaction, and conversion. 

In an analogous late-stage arylation approach, terminal alkyne 31 was envisioned as a versatile intermediate. Slow addition of 4-pentynoyl chloride to imine 3 and (n-Bu)3N at reflux (efficient condenser, 100°C, 12 h, 1 1 toluene heptane) afforded only trace amounts of 31. Reaction of 4-pentynoyl chloride with triethylamine in methylene chloride under preformed ketene conditions ( 78°C, 1 h), followed by addition of 3 and warming to — 10°C over 4 h, afforded a complex mixture of products. Since high-yield preparation of 31 remained elusive, access to internal alkynyl analogs (type 33) was accomplished by preassembly of the appropriate arylalkynyl acid substrate for the ketene-imine cycloaddition reaction (Scheme 13.9). 

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