2-Methyl-4-pentenoic acid

In an attempt to elaborate50 a synthetic access to DL-garosamine [126, 3-deoxy-4-C-methyl-3-(methylamino)-DL-arabinopyranose], the 1,5-lactone of 5-hydroxy-4-methyl-3-pentenoic acid (124) was oxy-aminated, to yield 2,3-dideoxy -C-methyl-3-p-toluenesulfonamido-DL-enyfhro-pentono-l,5-lactone (125). Introduction of a hydroxyl... 

Both [Pd(OAc)2] and [Pd(acac)2] were used as catalyst precursors, in the presence of PPh3 or PBun3. No catalysis occurred here in absence of the phosphorus ligand. When isoprene was carbonylated using [Pd(OAc)2] and PPh3 as catalyst precursor, dimerization of the alkene did not take place, the ester of 4-methyl-3-pentenoic acid being formed as the only product.529... 

A wide variety of unsaturated carboxylic acids have been allowed to react with HBr.101 Carboxylic acids with remote C—C double bonds react as simple alkenes.138,139 4-Pentenoic acid reacts with HBr neat or in a polar solvent to give exclusively 4-bromopentanoic acid, but the reaction in nonpolar solvents affords only 5-bromopentanoic acid.136 On the other hand, 5-methyl-4-hexenoic acid produces only the S-bromo acid. A similar pattern is followed by 3-butenoic, 3-pentenoic and 4-methyl-3-pentenoic acids. No matter what the substitution pattern, 2-alkenoic acids always favor the 3-bromo acid.113,136,140,141 Addition of HBr to cyclic a,3-unsaturated acids initially forms predominantly the product of trans diaxial addition which upon longer reaction time or higher temperature isomerizes to the trans product (equation 92).57,141,142 Similar observations have been made on bicyclic a.fj-unsaturated acids.141... 

Both [Pd(OAc)2] and [Pd(acac)2] were used as catalyst precursors, in the presence of PPhs or PBu"3. No catalysis occurred here in absence of the phosphorus ligand. When isoprene was carbonylated using [Pd(OAc)2] and PPhj as catalyst precursor, dimerization of the alkene did not take place, the ester of 4-methyl-3-pentenoic acid being formed as the only product. Because of its potential application to the synthesis of esters for lubricating oils, the dimerization-carbonylation of butadiene has received special attention. Basic phosphines such as PBu°3 and weakly basic tertiary amine solvents (quinoline, N,N-diethylaniline) were found to improve both the stability and activity of the catalyst system.In a further report in which PPr 3 was used as phosphorus ligand it was found that the addition of maleic anhydride caused a marked increase in the catalytic activity. It was believed that through coordination it stabilized the palladium(O) complexes formed against precipitation as metal. ... 

Methyl-3-pentenoic acid refluxed 4 hrs. with AICI3 and n-hexane as H-donor 4-methylpentanoic acid. Y 89%. F. e., also with ligroin instead of -hexane, s. A. G. Giumanini, A. Drusiani, and L. Plessi, J. Org. Chem. 40, 1844 (1975). 

Saturated carboxylic acids do not decarboxylate, but P,Y-unsaturated carboxylic acids do. Explain why, using a mechanism to show the decarboxylation of 3-butenoic acid. Use your mechanism to predict the product of decarboxylation of ( )-4-methyl-3-pentenoic acid. 

Later on structure 1 was modified to structure 2 (Fig. 2), since in the ozonolysis two moles of acetone and no 2-methylpropanal were produced (16,17). Also, hydrolysis affords 4-methyl-3-pentenoic acid rather than the 4-methyl-3-pentenoic acid expected from 1 (18,19). There was some confusion at one time, because of the isomerization possibility between these two acids. 

CO, and methanol react in the first step in the presence of cobalt carbonyl catalyst and pyridine [110-86-1] to produce methyl pentenoates. A similar second step, but at lower pressure and higher temperature with rhodium catalyst, produces dimethyl adipate [627-93-0]. This is then hydrolyzed to give adipic acid and methanol (135), which is recovered for recycle. Many variations to this basic process exist. Examples are ARCO s palladium/copper-catalyzed oxycarbonylation process (136—138), and Monsanto s palladium and quinone [106-51-4] process, which uses oxygen to reoxidize the by-product... 

Obviously, the use of a nonvolatile ionic liquid simplifies the distillative workup of volatile products, especially in comparison with the use of low-boiling solvents, where it may save the distillation of the solvent during product isolation. Moreover, common problems related to the formation of azeotropic mixtures of the volatile solvents and the product/by-products formed are avoided by use of a nonvolatile ionic liquid. In the Rh-catalyzed hydroformylation of 3-pentenoic acid methyl ester it was even found that the addition of ionic liquid was able to stabilize the homogeneous catalyst during the thermal stress of product distillation (Figure 5.2-1) [21]. This option may be especially attractive technically, due to the fact that the stabilizing effects could already be observed even with quite small amounts of added ionic liquid. 

Acetoxy-1,4- naphthoquinone [ 1,4-Naphthalenedione, 2-(aoetyloxy)-] 4-Methyl-3-pentenoic [3-Pentenoic acid, 4-methyl-] 2-Acetoxy-3-(y,y-dimethylallyl) [1,4 -Naphthalen ed i one, 2-(acetyloxy)-3-(3-methyl-2-butenyl)-] 73 4... 

Pentenoic acid 4-methyl-, 70 3 Penten 2-ol, 3 bromo, acetate, 35 3-Penten-2-ol, 3-bromo-4-methyl-, acetate,... 

C5H4N2O 1003-52-7) see Pyridoxine 2-cyano-3-methyl-2-pentenoic acid ethyl ester (C HijNOj 759-51-3) see Ethosuxiinide... 

Encapsulated rhodium complexes were prepared from Rh-exchanged NaY zeolite by complexation with (S)-prolinamide or M-tert-butyl-(S)-prolinamide [73,74]. Although these catalysts showed higher specific activity than their homogeneous counterparts in non-enantioselective hydrogenations, the hydrogenation of prochiral substrates, such as methyl (Z)-acetamidocinnamate [73] or ( )-2-methyl-2-pentenoic acid [74], led to low... 

A 1996 work deposited four different catalytic metals on a p-cyclodextrin— epichlorohydrin copolymer to prepare Pd(Pt, Rh, Ru)-P-cyclodextrin copolymer catalysts.8 These were used to catalyze the asymmetric hydrogenations of the C=C bonds of trans-2-methyl-2-pentenoic acid, and dimethyl itaconate. 

Iodolactonization of anti,syn-1 could result in four iodolactones, two resulting from face selectivity, and two resulting from diastereotopic olefin selectivity. In practice only three lactones are formed in a 142 4.7 1 ratio, with 4 being essentially the only product. In fact this kinetic iodolactonization proceeds with 147 1 olefin selectivity and 30 1 face selectivity, considerably higher than the selectivity observed in previous iodolactonization of 3-methyl-4-pentenoic acid (8, 257). Lac-tonization of 1 also shows cis-C4,C5 selectivity. 

Substrates 4-9 were chosen by Freeman to study the influence of steric bulk on the free activation energy. As discussed before the substituents also show an electronic effect and it is hard to separate both effects, but at least some comparisons can be made, e.g., for trans-crotonic acid 4 and 4,4-dimethyl-trans-2-pentenoic acid 9. The steric bulk of the t.-butyl group compared to a methyl group should be by far more important than the difference in the electronic effect. 

A more useful way of reducing esters to ethers is a two-step procedure applied to the reduction of lactones to cyclic ethers. First the lactone is treated with diisobutylaluminum hydride in toluene at —78°, and the product - a lactol - is subjected to the action of triethylsilane and boron trifluoride etherate at —20° to —70°. y-Phenyl-y-butyrolactone was thus transformed to 2-phenyltetrahydrofuran in 75% yield, and 5-lactone of 3-methyl-5-phenyl-5-hydroxy-2-pentenoic acid to 4-methyl-2-phenyl-2,3-dihydropyran in 72% yield [1034]. 

Acylation of 179 with 2,2-difluoro-3-methyl-4-pentenoic acid anhydride yields ot-amino ketones 180 that can serve as intermediates to prepare pseudopeptides such as peptidyl ot,ot-difluoroalkylketones 181 (Scheme 7.54) or ketomethylene pseudo-peptides. ... 

Similarly the enantiomerically pure bicyclic A -propionyl lactam 9 can be enolized and reacted with allyl iodide to give a 56% yield of the alkylation product 10 (d.r. 98 2), which when hydrolysed furnishes (7 )-2-methyl-4-pentenoic acid (11)5. 

Methyl Z-2-(bromomethyl)-4-methylpent-2-enoate 2-Pentenoic acid,... 

ETHYL (1-ETHYLPROPEN YL)-METHYLCYAN OACETATE (3-Pentenoic acid, 2-cyano-3-ethyl-2-methyl-, ethyl ester)... 

Table 4.81 shows the empirical increments obtained for substituents in position i relative to an olefinic carbon denoted as k. Correction terms S are required for cis and geminal substituents. As an application of the increments in Table 4.81 the olefinic carbon shifts of (Z)-4-methyl-2-pentenoic acid are predicted ... 

Pentenoate Methyl 2.2-Difluoro-E10b2. 203f. (Oil - OR) 4-Pentenoic Acid 2.2-Difluoro-3(or4)-methyl- E10b2, 224f. (C1F2C-C0-C)-CH2-C R = CH2/RjSi — Cl/Zn)... 

CO-F -> 2-M) 4-Pentenoic Acid 3-Methyl-2-trifluoromethyl- E10b2. 222f. 

Diastereoselective aza-Claisen rearrangement,1 The oxazole 1 prepared by reaction of L-valinol with propionic acid is readily convertible into an N-allylketene acetal (2), which rearranges at 150° to 3 in 94% de and 80% overall chemical yield. Acid catalyzed hydrolysis of 3 gives (R)-( - )-2-methyl-4-pentenoic acid (4) (85% yield) with recovery of L-valinol. 

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