19361-58-1

Upstream product

• 7235-40-7 beta-carotene 
• 6811-73-0 β-Carotin 
• 116-31-4 all-trans-Retinal 
• 83601-92-7 7-cis-β-carotene 
• 13312-52-2 9-cis-β-carotene 
• 4481-69-0 15,15'-didehydro-β,β-carotene 

Downstream Products

• 7235-40-7 beta-carotene 
• 6811-73-0 β-Carotin 

Relevant academic research and scientific papers

Reductive coupling of aldehydes by H2S in aqueous solutions, a C-C bond forming reaction of prebiotic interest

We report here a novel reductive coupling reaction of conjugated, non- or poorly enolizable aldehydes induced by H2S and operative in aqueous solutions under prebiotically relevant conditions. This reaction leads from retinal to β-carotene, and from benzylic aldehydes to the corresponding diarylethylenes. This novel reaction also opens a new potentially prebiotic pathway leading from glyoxylic acid to various compounds that are involved in the reductive tricarboxylic acid cycle. This C-C bond forming reaction of prebiotic interest might have been operative, notably, in the sulfide-rich environments of hydrothermal vents, which have been postulated as possible sites for the first steps of organic chemical evolution.

Mild oxidative cleavage of β,β-carotene by dioxygen induced by a ruthenium porphyrin catalyst: Characterization of products and of some possible intermediates

Mild oxidative cleavage of β,β-carotene by dioxygen is induced by a ruthenium tetramesitylporphyrin catalyst, and it leads to the full possible range of β-apocarotenals and β-apocarotenones. The slow reaction kinetics allow the sequence of events leading to double bond cleavage over a period of 24 h to be monitored by HPLC-DAD and HPLC-MS.

Semiconductor photocatalysis: Photodegradation and trans-cis photoisomerization of carotenoids

In the presence of semiconductor CdS or ZnO particles, irradiation (>350 nm) of all-trans-β-carotene (II) in dichloromethane leads to rapid degradation of the carotenoid, which is relatively stable in the absence of the semiconductors. Canthaxanthin (I), however, undergoes significant photocatalyzed degradation only on ZnO, not on CdS. High-performance liquid chromatographic studies indicate that CdS catalyzes trans-cis photoisomerization of both I and II. As in the photoisomerization in the absence of semiconductor, the major cis isomers have the 9-cis and 13-cis configuration, but, under otherwise the same condition, the ratio of cis/trans isomers has doubled. In contrast to CdS, ZnO does not catalyze the photoisomerization of either I or II, although it enhances their rate of degradation. A photoisomerization mechanism involving carotenoid radicals formed by reaction with interstitial sulfur on the CdS surface is proposed.

Thermal interconversions among 15-cis-, 13-cis-, and all-trans-β-carotene: Kinetics, arrhenius parameters, thermochemistry, and potential relevance to anticarcinogenicity of all-trans-β-carotene

Rates of thermal, cis-trans rearrangement among all-trans-, 15-cis-, and 13-cis-β-carotene have been measured at temperatures in the range 37-69°C. From the resulting specific rate constants, Arrhenius and Eyring parameters are derived. Positions of equilibrium are estimated experimentally and by force field calculations based on the Allinger MM2 program as improved by Roth (MM2-ERW), while enthalpies of activation for cis-trans isomerization to 11-, 9-, and 7-cis-β-carotenes are estimated by application of the Roth program augmented by the inclusion of the quantum mechanical program of Malrieu et al., EVBH (effective valence-bond Hamiltonian), expanded to encompass longer polyenes. Implications of the interaction of strain and delocalization in the rotation about the 7,8 double bond are presented. A procedure has been developed for the small scale preparation of 13-cis-β-carotene by heating all-trans-β-carotene at 80°C for 8 h. Kinetically and thermodynamically accessible at 37°C, 15-cis- or 13-cis-β-carotene or both become candidates for the role of true anticarcinogenic agent, whereupon all-trans-β-carotene would be relegated to the role of reservoir for the active species.

Carbonyl coupling reactions catalytic in titanium and the use of commercial titanium powder for organic synthesis

The high thermodynamic stability of titanium oxides formed as the inorganic byproducts in McMurry-type reactions has so far prevented the development of a catalytic procedure for such reductive carbonyl coupling processes. Similarly, a tightly bound oxide layer passivates the surface of commercial titanium, which is unreactive toward organic substrates under conventional conditions. This paper outlines a way to overcome both of these problems. Thus, oxoamides 1a-h can be reductively cyclized to indoles 2a-h using only catalytic amounts of low-valent titanium if the reaction is carried out in the presence of a chlorosilane. Specifically, the method is based upon the in situ generation of an activated titanium species from TiCl3 and Zn in the presence of the substrate, followed by regeneration of titanium chloride from the titanium oxides formed via ligand exchange with the admixed chlorosilane. Its proper choice is crucial for obtaining both good turnover numbers and clean conversions. Depending on the product structure, (TMS)Cl, ClMe2SiCH2CH2SiMe2Cl (5), or ClMe2Si(CH2)3CN (6) was found to be best suited. Similarly, chlorosilanes also effect the activation of commercial titanium powder which may then be used as a performant off-the-shelf reagent for various types of carbonyl and acetal coupling reactions, for the deoxygenation of epoxides and for the reductive cyclization of oxoamides or oxoesters to indoles, benzofurans, and 2-quinolones. Under these conditions retinal can be reductively dimerized to β-carotene in good yield. Moreover, the titanium/ chlorosilane reagent combination exhibits a strong template effect, allowing macrocyclization reactions without recourse to high dilution. Up to 36-membered rings have been closed in that way. 29Si NMR studies provide some insight into the elementary steps responsible for the degradation of the surface oxide layer on titanium by the chlorosilane. The effect of Lewis acid additives on the course of the coupling processes is discussed.

Kinetic Model for Studying the Isomerization of α- and β-Carotene during Heating and Illumination

The thermoisomerization and iodine-catalyzed photoisomerization of all-trans-α- and all-trans-β-carotene were kinetically studied using regression models. Carotene samples were heated at varied temperatures or exposed to a 20 W light for varied lengths of time. Isomerization and degradation reactions were monitored using HPLC with diode array detection. Four cis isomers of β-carotene and three cis isomers of α-carotene were separated and detected. The degradations of both carotenes under heating at 150 deg C or iodine/light treatment may fit the reversible first- order model. 9-cis and 13-cis were the major β-carotene isomers formed during heating, while 13,15-di-cis was favored during iodine-catalyzed photoisomerization. The formation of 9-cis and 13-cis form all-trans-α-carotene was dependent upon the extent of heat or iodine/light treatment, and the latter was formed in greater amount under either treatment. Keywords: α-Carotene; β-carotene; thermoisomerization; photoisomerization; kinetic study

Triplet-Sensitized and Thermal Isomerization of All-Trans, 7-Cis, 9-cis, 13-Cis, and 15-Cis Isomers of β-Carotene: Configurational dependence of the Quantum Yield of Isomerization via the T1 State

The products of triplet-sensitized photoisomerization (excitation at 337 nm of the sensitizer, anthracene) and thermal isomerization of β-carotene in n-hexane, starting from the all-trans, 7-cis, 9-cis, 13-cis, and 15-cis isomers, were analyzed by HPLC.Direct photoisomerization (excitation at 488 and 337 nm) was also examined for comparison.Three different isomerization patterns were found in both triplet-sensitized and thermal isomerization: pattern A, cis to trans isomerization around each cis bond; pattern B, trans to cis isomerization in the central part of the conjugated chain; and pattern C, cis to another cis isomerization.In the T1 state, the pattern A isomerization was predominant even for the peripheral-cis (7-cis and 9-cis) isomers and its efficiency was extremly high for the central-cis (13-cis and 15-cis) isomers.In the S0 state, the pattern B isomerization, instead, was predominant for the peripheral-cis isomers, and the pattern A isomerization was predominant only for the central-cis isomers.The quantum yields of triplet-sensitized isomerization (decrease of the starting isomer per triplet species generated) were determined to be as follows: all-trans, 0.04; 7-cis, 0.12; 9-cis, 0.15; 13-cis, 0.87; and 15-cis, 0.98.In direct photoisomerization, the quantum yield of isomerization at 488-nnm (337 nm) excitation was 4 (3) orders of magnitude lower than the above values, the relative values among the isomers being similar to the above.Further, the overall isomerization patterns of direct photoexcitation were similar to those of triplet-sensitized isomerization, supporting the idea that isomerization takes place via the T1 state even in the case of direct photoexcitation.Carbon-carbon ? bond orders of model polyenes in the T1 and S0 states were calculated by using the Pariser-Parr-Pople CI theorie; bond lengths were optimized by using a bond order-bond length relationship.Isomerization characteristics in the T1 and S0 states observed were discussed based on the results of the calculations.