Prins condensation

With Ga-Beta it was found that, when the Si/Ga ratio increased from 10 to 40, the number of strong sites decreased drastically for Si/Ga between 10 and 25 and then reached a plateau above Si/Ga = 25 [53], The strength and density of acid sites in H(Ga, La)-Y were also found to be lower than those in HY crystals of the type used in FCC preparation (LZY-82) [250], Similar catalytic selectivities were obtained for both Ga-ZSM5 and A1-ZSM5 in Prins condensation of isobutylene with formaldehyde. Catalytic tests coupled with microcalorimetric measurements have shown that medium to weak acid strength sites favor the selectivity to isoprene [254],... 

Dumitriu, E., On, D. T., Kaliaguine, S. Isoprene by Prins condensation over acidic molecular sieves. J. Catal. 1997,170,150-160. 

By way of review, the Prins reaction (Scheme 8.20) comprises addition of a carbonyl group to an olefin followed by capture of a nucleophile by the other end of the double bond (20-1). A side reaction consists of addition of carbonyl oxygen (20-2). Yet another photolysis, this one on 19-5, severs the bond between the carbonyl and the adjacent quaternary carbon atom to the unsaturated aldehyde 21-1 (Scheme 8.21) this is admixed with the product of 21-2 from addition via oxygen. Treatment of the mixmre of these products with mild acid leads to intramolecular Prins condensation of the aldehyde in 21-1 with the C13-C14 double bond. Capture of a nucleophile, in this case water, from the less hindered face installs the critical 14a-hydroxyl function. The (9-addition product 21-2 presumably cycles back to 21-1, which the goes on to product. The 12)8-hydroxy product predominates over its 12a-isomer in a 2 1 ratio. 

Besides the already mentioned acidic aluminum chloride catalysts, alternative Friedd-Crafts catalysts such as supported acidic tin catalysts have also been developed. The tin-based catalysts were prepared by a method which closely resembled the already mentioned two-step grafting method devised for the aluminum chloride catalyst. Here, SnCU was anchored on silica materials modified with tetraalkylammonium chloride moieties obtained for example, from reaction with [3-(trimethoxysrlyl)propyl]octadecyldimethylammonium chloride, thereafter, reaction of the Lewis acid with the chloride moieties leads to formation of pentacoordinated anionic tin species forming catalytically active complexes (i.e. [R4N][SnCl5] species), associated with the surface. The supported tin catalysts were employed for condensation reactions of olefins with aldehydes forming unsaturated alcohols (Prins condensation. Scheme 5.6-2) [76]. 

Scheme 5.6-2 Prins condensation of isobutene with formaldehyde (MBD 3-methylbutane-l,3-diol, DMD 4,4-dimethyl-l,3-diol, MBOH 3-methyl-3-buten-l-ol catalyzed by tin (IV) chloride species [75].

Y. Wang, F. Wang, Q. Song, Q. Xin, S. Xu, J. Xu, Heterogeneous ceria catalyst with water-tolerant Lewis acidic sites for One-Pot synthesis of 1,3-diols via prins condensation and hydrolysis reactions, J. Am. Chem. Soc. 135 (2013) 1506—1515. 

Catalytic tests of Prins condensation of isobutylene with formaldehyde over iron-substituted MFI catalysts have shown that medium to weak acid strength sites favor the selectivity to isoprene [241]. [Ga]-ZSM5 was also tested as a catalyst for this condensation, but its catalytic selectivity was rather close to that of [A1]-ZSM5 [241]. 

H.J. Prins, Condensation of formaldehyde with some unsaturated compounds, Chem. Weekbl 16 (1919) 1072-1073. 

Scheme 1.11 Prins Condensation Reaction of (3-Pinene and Paraformaldehyde.

E. Dumitriu, V. Hulea, I. Fechete, C. Catrinescu, A. Auroux, J.F. Lacaze, C. Guimon et al., Prins condensation of isobutylene and formaldehyde over Fe-sUicates of MFI structure. Appl. Catal. A Gen. 181, 15-28 (1999)... 

PdCb-CuCb catalyzes the condensation of branched-chain alkenes with formaldehyde to give the l,3-dioxanes 96a and 96b (Prins reaction)[73]. The yields are much higher than in the conventional acid-catalyzed Prins reaction. 

An important synthetic process for forming a new carbon—carbon bond is the acid-catalyzed condensation of formaldehyde with olefins (Prins reaction) ... 

Condensation of vinyl chloride with formaldehyde and HCl (Prins reaction) yields 3,3-dichloro-l-propanol [83682-72-8] and 2,3-dichloro-l-propanol [616-23-9]. The 1,1-addition of chloroform [67-66-3] as well as the addition of other polyhalogen compounds to vinyl chloride are cataly2ed by transition-metal complexes (58). In the presence of iron pentacarbonyl [13463-40-6] both bromoform [75-25-2] CHBr, and iodoform [75-47-8] CHl, add to vinyl chloride (59,60). Other useful products of vinyl chloride addition reactions include 2,2-di luoro-4-chloro-l,3-dioxolane [162970-83-4] (61), 2-chloro-l-propanol [78-89-7] (62), 2-chloropropionaldehyde [683-50-1] (63), 4-nitrophenyl-p,p-dichloroethyl ketone [31689-13-1] (64), and p,p-dichloroethyl phenyl sulfone [3123-10-2] (65). 

Other nucleophilic additions conducted in aqueous media can be found in the literature (Lubineau et al., 1994 Strauss, 1999). These reactions will include the benzoin condensation, the Prins reaction, and the Wittig-Horner reaction, and the Baeyer-Villi-ger oxidation. 

The method ZC3Z + C is used for the preparation of reduced pyrimidines, oxazines and thiazines as well as for dioxanes, dithianes and oxathianes as mentioned above (e.g. 258 — 257, 259 Z, Z = NH, O, S). The Prins reaction yields 1,3-dioxanes (77S661) it involves the acid-catalyzed condensation of alkenes with aldehydes with 1,3-diols as intermediates. 

Prins-pinacol condensation of a (Z)-a,p-unsaturated aldehdye and an (S)-carvone-derived alkynyl dienyl diol as illustrated below provided the formyl tetrahydroisobenzofuran as a single diastereomer in 84% yield in two steps <03JA6650>. 

In the Cannizzaro reaction (62), which involves self-condensation of aldehydes that have no a-hydrogen atoms, the nucleophile is represented best as a hydride ion in the Prins reaction (26), the nucleophile is an olefin in the aldol condensation (63) and reaction of methyl acetate with formaldehyde (62), the nucleophile is a methylene group a- to a... 

The acidic 10 and 12 membered ring zeolites (H-MOR, ZSM-5, ZSM-11) can also be used to catalyze the condensation of alkenes with aldehydes to form unsaturated alcohols, acetals etc. (Prins reaction)[92]. Chang et a/. [93] showed that this reaction involves in the initial step the activation of the aldehyde by a Bronsted acid site to generate an electrophilic species. The condensation with, e.g., isobutene leads then to a primary alcohol with a positive charge at the tertiary carbon atom. Elimination of water and addition of further aldehyde molecules may lead to a broad variety of products. Some of these reactions can be effectively blocked by chosing zeolites with the appropriate pore size [94,95]. 

The Prins-pinacol rearrangement was utilized during the first enantioselective total synthesis of briarellin diterpenes by L.E. Overman and co-workers. The cyclohexadienyl diol substrate was condensed with a (Z)-a,p-unsaturated aldehyde at low temperature in the presence of catalytic amounts of acid and MgS04 as dehydrating agent. The initially formed acetal was then exposed to 10 mol% of SnCU to afford the desired tetrahydroisobenzofuran as a single stereoisomer that was later converted to briarellin F. 

The enantioselective total synthesis of the polysubstituted tetrahydrofuran (-)-citreoviral, the unnatural enantiomer, was synthesized by L.E. Overman et al. The Prins-pinacol rearrangement of an allylic 1,2-diol with an unsymmetrical ketone proceeded with high stereoselectivity. The jb/s(trimethylsilyl)-1,2-diol was condensed with the dimethyl acetal of the unsymmetrical ketone in the presence of catalytic amounts of TMSOTf, which yielded a nearly 1 1 mixture of the corresponding acetal and rearrangement product. The acetal was converted to the desired tetrahydrofuran product upon exposure to tin tetrachloride. 

Prins reaction Acid-catalyzed condensation of alkenes with aldehydes. 364... 

Prins, H. J. The reciprocal condensation of unsaturated organic compounds. Chem. Weekblad 1919,16, 1510-1526. 

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