Benzaldehydes methoxybenzaldehyde

The aprotic diazotisation of tetrachloroanthranilic acid in the presence of benzaldehyde or />-methoxybenzaldehyde results in the formation of the 1,3-benzodioxan derivatives (131, R = Ph) and (131, R = >-C gH 4-OMe) respectively 155). The absence of products analogous to (129) in these reactions suggests that the formation of the compounds (131) do involve tetrachlorobenzyne. Some indication of the mechanism of these reactions was given by the fact that no analogous adduct has been isolated in attempted reactions of tetrachlorobenzyne with p-nitrobenzaldehyde. However, in the presence of acetone we obtained a low yield of the compound (132). 

The synthesis of 3-H-oxazol-2-ones was described by Nam et al. [69]. The substituted benzoin 89 was formed from the coupling of 3,4,5-trimethoxy-benzaldehyde 18 with 3-nitro-4-methoxybenzaldehyde, Scheme 22. Reaction with PMB-isocyanate and subsequent cyclization gave the protected oxazolone derivative 90. The PMB group was removed by reflux in TFA and reduction of the nitro-group was performed using Zn to give the combretoxazolone-aniline 91. 

Fig. 3.1.8 E nantioselective synthesis of benzoins in a two-phase system. KP, buffer (25 mb, 50 mM, pH 8), ThDP (0.5 mM, MgCh (0.5 mM), MTBE (15 mb), substrate (40 mM with respect to the whole reaction volume of 40 mb 40 mM benzaldehyde or 20 mM 2-chlorobenzaldehyde and 20 mM 3-methoxybenzaldehyde, respectively). Concentrations of reactants in the diagram are given for the organic phase only.

Using only benzaldehyde as substrate (see Fig. 3.1.8a), (R)-benzoin can be obtained on a 200 mg scale from a 40 mb two-phase system. This corresponds to a volumetric productivity of 53 g L d for the organic phase, or 20 g d with respect to the overall reaction volume. When using 2-chlorobenzaldehyde and 3-methoxybenzaldehyde as substrate in equimolar amounts, (R)-2-chloro-3 -methoxybenzoin is formed as the main product with approximately 80% selectivity (see Fig. 3.1.8b). The symmetric benzoins (2,2 -dichlorobenzoin, 3,3 -dimethoxybenzoin) are formed as side-products. The main product is obtained on a 150 mg scale, which corresponds to a volumetric productivity of 40 g L d with regard to the organic phase. 

A mixture of 205 g POCl, and 228 g N-methylformanilide was allowed to incubate at room temperature until there was the development of a deep claret color with some spontaneous heating. To this, there was added 70.8 g 2,3-dimethyl-anisole, and the dark reaction mixture heated on the steam bath for 2.5 h. The product was then poured into 1.7 L H20, and stirred until there was a spontaneous crystallization. These solids were removed by filtration, H20 washed and air dried to give 77.7 g of crude benzaldehyde as brown crystals. This was distilled at 70-90 °C at 0.4 mm/Hg to give 64.8 g of 2,3-dimethyl-4-methoxybenzaldehyde as a white crystalline product with a mp of 51 -52 °C. Recrystallization from MeOH produced ananalyticalsamplcwithampof55-55.5°C. Anal.(C 0H12O2)C,H. Themalononitrile derivative (from the aldehyde and malononitrile in EtOH with a drop of triethylamine) had a mp of 133-133.5 °C from EtOH. Anal. (C Hl2N20) C,H,N. Recently, this aldehyde has become commercially available. 

Reaction Steps 3a and 3b also can be used to rationalize the observed para-substituent effects presented in Table III the more electron-releasing, para-substituted benzaldehydes retard the rate of oxidative addition (18) for RhCl(PPh3)3. Therefore, p-methyl- and p-methoxybenzaldehyde are expected to be decarbonylated slower than the unsubstituted benzaldehyde, as is observed in Table III. (This argument requires that Reaction 3a be saturated to the right, which is expected, in neat aldehyde solvent with electron-releasing, para-substituted benzaldehydes.) The unexpected slower rate for p-chloro-benzaldehyde could be accounted for ifK for this aldehyde is small and saturation of equilibrium in Equation 3a is not achieved. Note that fcobs is a function of K and k (see Equation 4b) under this condition. It is also possible that the rate-determining step is different for this aldehyde. Present research includes a careful kinetic analysis using several aldehydes so that K and k can be determined independently. 

An intramolecular Mannich-type cyclization of l,3-dimethyl-6-(2-aminophenylthio)uracil (120) has been utilized for the synthesis of 5, 6-dihydropyrimido[4,5-b][ 1,5]benzothiazepine-2,4( 1H,3//)-diones (121) this synthesis was realized by reaction of 120 with an excess of formaldehyde, benzaldehyde, or p-nitro- or p-methoxybenzaldehyde in chloroform in the presence of a catalytic amount of p-toluenesulfonic acid under reflux for 4-10 hours. The thiazepine cyclization using aliphatic aldehydes other than formaldehyde did not give satisfactory results. In these cases the reaction resulted in the formation of a dimeric product that probably... 

Acetoxy-3-methoxy-2-nitrobenzaldehyde, 3260 4-Acetoxy-3-methoxybenzaldehyde, 3284 f Acrylaldehyde, 1142 4-Azidobenzaldehyde, 2693 f Benzaldehyde, 2727 f Butyraldehyde, 1602 5 -Chloro-2-nitrobenzaldehyde, 2648 4-Chloro-3-nitrobenzaldehyde, 2647... 

D Auria and coworkers investigated the photocycloaddition of 5-methyl-2-furyl-phenylmethanol 92 with benzophenone resulting in two adducts 93 and 94 in a 1 1 ratio while the addition to 4,4/-dimethoxy-benzophenone, benzaldehyde or 4-methoxybenzaldehyde, respectively, gave merely the adducts 93 (Sch. 27) [88]. 

Condensations of erythritol with benzaldehyde,78,78 o-, wi-andp-chloro-benzaldehyde,18 p-methylbenzaldehyde,18 p-methoxybenzaldehyde,18 o-, m- and p-nitrobenzaldehyde,18,87 3-nitro-4-chlorobenzaldehyde,18 acetaldehyde,74 chloroacetaldehyde,74 acetone,1718 formaldehyde,78 and val-eraldehyde76 have been reported, but in no case has the structure of the product been determined. The physical constants of these acetals and ketals are recorded in Table VII. The photo-sensitivity of o-nitrobenzyl-idene-erythritols has been discussed on page 149. 

Working across the preceding pages from left to right, we may derive from the four aldehydes at least one of the chemical names for each of the remaining products. (These are only shown when commonly used.) Anisaldehyde, for example, is sometimes referred to as para-methoxy benzaldehyde, and vanillin can be referred to aspara-hydroxy-/raeta-methoxy benzaldehyde, or 4-hydroxy-3-methoxybenzaldehyde. (Not surprisingly the common name is the one preferred.)... 

Difunctional compounds will have 3 values larger than either of the mono-substituted compounds. For example, for benzaldehyde 3 = 0.23 and for methoxybenzene 3 = 0.15, but the 3 value for methoxybenzaldehyde will be larger than 0.23 by an increment which depends upon the difference between values (A 3) of the mono substituted compounds as follows ... 

Demethylation of methoxybenzaldehydes. BI3 is more reactive than BCI3 (2, 34-35 4, 43) and cleaves methoxyl groups of aromatic aldehydes regardless of the position. BBr, is also effective but this reagent can convert benzaldehydes into benzal bromides. ... 

SYNS 2-ANISALDEHYDE BENZALDEHYDE, 2-METHOXY-(9CI) o-METHOXYBENZALDEHYDE 2-METHOXYBENZALDEHYDE 6-METHOXY-BENZALDEHYDE 2-METHOXYBENZENE-CARBOXALDEHYDE SALICYLALDEHYDE METHYL ETHER... 

The second-order rate constants for the reaction of OH radical with meta- and para-isomers of hydroxy-, methoxy-, chloro- and nitro-benzaldehydes are in the range (2.8 to 12) x 10 dm mol s . The higher rate in methoxybenzaldehyde is attributed to the activation of the ring by the electron-donating -OCH3 group. 

A first set of experiments, the study of the protonation of enolates obtained from benzaldehyde Schiff bases and Lithium Diisopropylamide, showed that the asymmetric induction was not significantly affected by the size of the R moiety of the amino acid (R = Me, Et, i-Pr, n-Bu, f-Bu, Ph ee = 44-56%). The two main factors improving the enantioselection were the Ar substituent of the Schiff base and the lithium amide used for the deprotonation. The following results (Table 1) indicate clearly that the enantioselectivity increases with the electron-donating power of substituents para to the Schiff base (eq 3), leading to 70% ee with the Schiff base of p-methoxybenzaldehyde derived from phenylglycine. ... 

Arylcarbenes are formed from benzaldehyde and some of its derivatives if the Clemmensen reduction is performed using boron trifluoride or another Lewis acid instead of hydrochloric acid. If the reaction is carried out in the presence of an alkene, which is often used as solvent, addition to the C-C double bond takes place and cyclopropane formation results in low to fair yields. The arylcyclopropanes are always formed as mixtures of stereoisomers and, in all cases but two, the endo-isomcr is significantly predominant. Thus, when a mixture of 4-methoxybenzaldehyde, boron trifluoride-diethyl ether complex and a considerable excess of cyclohexene was allowed to react with amalgamated zinc, 7-(4-methoxyphenyl)bicy-clo[4.1.0]heptane (1) was obtained in 60% yield. 

---