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Vinyl aldehydes

Aliphatic, aromatic and vinylic aldehydes can be employed in this reaction with similar yields and enantioselectivities. When chiral aldehydes are utilized, excellent diastereoselectivity is obtained for matched cases, whereas mismatched cases yield products with moderate to good diastereoselectivity (Scheme 9.13a) [67]. The limitation of the methodology is that only terminal vinylepoxides can be obtained. [Pg.324]

Stable aryl boronates derived from tartaric acid catalyze the reaction of cyclo-pentadiene with vinyl aldehyde with high selectivity. Chiral acyloxy borane (CAB), derived from tartaric acid, has proved to be a very powerful catalyst for the enantioselective Diels-Alder reaction and hetero Diels-Alder reaction. Scheme 5 23 presents an example of a CAB 73 (R = H) catalyzed Diels-Alder reaction of a-bromo-a,/i-cnal 74 with cyclopentadiene. The reaction product is another important intermediate for prostaglandin synthesis. In the presence of... [Pg.283]

Various catalytic or stoichiometric asymmetric syntheses and resolutions offer excellent approaches to the chiral co-side chain. Among these methods, kinetic resolution by Sharpless epoxidation,14 amino alcohol-catalyzed organozinc alkylation of a vinylic aldehyde,15 lithium acetylide addition to an alkanal,16 reduction of the corresponding prochiral ketones,17 and BINAL-H reduction18 are all worth mentioning. [Pg.415]

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. [Pg.132]

This procedure illustrates a general method for the preparation of aryl, benzyl, alkynyl, and vinyl aldehydes.1 2 4 5 6 Table I gives the aldehydes which have been prepared from the corresponding Grignard reagents by conditions similar to those described here. [Pg.93]

A series of conjugated polyenes capped with chromophores and containing an androstane spacer were synthesized by Wittig or Wittig-type olefinations from epi-androsterone 5150. For example, vinyl carboxaldehyde 52, prepared from 51 in 60% yield as shown in equation 32, was treated with 9-anthrylmethylphosphonium bromide and n-butyllithium to give diene 53. Exocyclic diene 53 was subsequently oxidized to vinyl carboxaldehyde 54. The androsterone vinyl aldehyde intermediate could either be treated with a tetraphenylporphyrinpolyenyl phosphonium ylide, or, as shown below, the phosphonium salt of the androsterone (55) could be reacted with TPP polyeneal 56. The desired all-(E) isomer, 57, was obtained from the ( )/(Z)-isomeric mixture by chromatographic purification. [Pg.712]

S-Aryltelluro vinyl aldehydes and ketones have been prepared by treating j -chlorovinyl carbonyl compounds or /(-acylvinyl triethyl ammonium chlorides with arene teUurolate... [Pg.80]

Chiral to side-chain units can also be obtained by various catalytic and stoichiometric asymmetric synthesis as well as by resolution (30). Scheme 14 shows the preparation of these side-chain units using kinetic resolution by the Sharpless epoxidation (31), amino alcohol-catalyzed organozinc alkylation of a vinylic aldehyde (32), lithium acetylide ad-... [Pg.164]

The synthesis of optically active polymers is an important area in macromolecular science, as they have a wide variety of potential applications, including the preparation of CSPs [31-37]. Many of the optically active polymers with or without binding to silica gel were used as CSPs and commercialized [38]. These synthetic polymers are classified into three groups according to the methods of polymerization (1) addition polymers, including vinyl, aldehyde, isocyanide, and acetylene polymers, (2) condensation polymers consisting of polyamides and polyurethanes, and (3) cross-linked gels (template polymerization). The art of the chiral resolution on these polymer-based CSPs is described herein. [Pg.327]

Synonyms 2-propenal, acraldehyde, vinyl aldehyde Formula CH2=CH-CHO an aldehyde MW 56.07 CAS [107-02-8] used to control aquatic weed, algae, and slime, and in leather tanning colorless, volatile liquid boils at 53°C freezes at -87°C density 0.843 g/mL at 20°C soluble in water mixes with alcohol and ether. [Pg.276]

Ally 1 Halides to Allyl Alcohols, Vinyl Aldehydes, Vinyl Ketones... [Pg.485]

Substituted phenethyl isocyanates undergo cyclization to lactams when treated with BF3 Et20 [65]. Vinyl ether epoxides (Eq. 37) [66], vinyl aldehydes [67], and epoxyjS-keto esters [68] all undergo cyclization with BF3 Et20. [Pg.100]

The reaction of amines with cyclopropenones appears to be extremely sensitive to the reaction conditions Ammonia reacts with diphenylcyclopropenone at room temperature to yield the isomeric /3-lactams 56 and 57, whereas the vinyl aldehyde 58 is produced at — 33°C. These results can be rationalized in terms of the intermediate 59 which would result from conjugate addition of the nucleophile at carbon (equation 56). [Pg.1553]

Table 2. Synthesis of IV-benzoyl- or sulfonyl- isothiazolium-2-imines 71,71 and 2-amino-isothiazolium perchlorates 72,73 from [3-thiocyanato-vinyl aldehydes 55a,e,g... Table 2. Synthesis of IV-benzoyl- or sulfonyl- isothiazolium-2-imines 71,71 and 2-amino-isothiazolium perchlorates 72,73 from [3-thiocyanato-vinyl aldehydes 55a,e,g...
The IR spectra serve as useful and easy method to identify perchlorate and functional groups and to differentiate between the p-thiocyanato vinyl aldehydes and the salts. [Pg.262]

Oxidation of the epimeric dihydro aldehydes 115 with freshly prepared silver oxide and esterification of the resulting epimeric acids 121 afforded the epimeric esters 123 [m/e 211 (M ), m/e 138 (base peak)]. In the same manner the quinuclidinic vinyl esters 124 [m/e 209 (M" ), m/e 136 (base peak)] were obtained from the vinyl aldehydes 116. Condensation of the esters 124 with 6-methoxy-4-quinolyllithium (3) gave a mixture of quininone (8) and quinidinone (9). [Pg.204]

In our new antithetic plan (Scheme 21), Weinreb s oxazolidinone 77 would remain a key synthetic objective. However, the Hoveyda-Grubbs reaction would now be applied to the diene 88. The new route would also block 0(4) of the vinyl aldehyde precursor with a TES ether to prevent hemiacetal formation from occurring. The crucial Vasella... [Pg.377]

An earlier investigation (23) demonstrated that the Vilsmeier-Haack reaction of the ArCOCHj type compounds gives the monoformylated compounds or the corresponding P-chloro-vinyl aldehydes. It was found, however, that in the case of o-hydroxyacetophenones, the methyl group was doubly formyl-ated by a Vilsmeier reagent to give our first target compounds, 4-oxo-4H-l-benzopyran-3-carboxaldehydes ( ) in one step ( 1, J ). The reason why double formylation took... [Pg.127]

Reactions of CpMo(CO)3Na and allylic halides or tosylates in THF afford CpMo(CO)3(Ti -allyl), and subsequent decarbonylation of these products by anhydrous McjNO or by photolysis give ii-allyl compounds. By this method, allyl compounds CpMo(CO)2(Jt-l-R-allyl) (R = H, alkyl, aryl, vinyl, aldehyde, COMe, COOMe) are obtained with... [Pg.147]

Pd-catalyzed synthesis of readily isolable jd-lactones 112 from ketene and 4-substituted vinyl aldehydes has been successfully achieved. Compound 112 was then isomerized to the corresponding 3,6-dihdyro-2-(fJ)-pyran-2-ones 113 under an atmosphere of nitrogen at different temperature (Scheme 38) (2000JCS(CC)73, 2002T5215). The generation of lactone... [Pg.211]

More recently, the same group has developed a one-pot sequence cobalt-catalyzed 1,4-hydrovinyIation/aIlylboration. The scope of the reaction was explored for a wide range of aUphatic, aromatic, heteroaromatic, and vinylic aldehydes affording interesting building blocks, for the synthesis of tetrasubstituted tetrahydropyrans in subsequent synthetic steps, with excellent yields and anft-diastereoselectivity as represented in Scheme 4.2 [5a]. [Pg.127]


See other pages where Vinyl aldehydes is mentioned: [Pg.329]    [Pg.124]    [Pg.112]    [Pg.176]    [Pg.53]    [Pg.124]    [Pg.329]    [Pg.211]    [Pg.329]    [Pg.291]    [Pg.204]    [Pg.204]    [Pg.172]    [Pg.124]    [Pg.242]    [Pg.29]    [Pg.268]    [Pg.147]    [Pg.133]    [Pg.231]   
See also in sourсe #XX -- [ Pg.228 ]




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