Sorbate, methyl

Notably, not only electron-rich dienes, but also electron-deficient dienes nicely participate in the reaction and react benzaldehyde with similar ease and in a similar sense of stereoselectivity. For example, methyl sorbate provides the 1,2-anti isomer exclusively in good yield with excellent regio- and stereoselectivity (run 7). The regioselectivity reacting at Cl of the diene skeleton might stem from electronic factors rather than from other factors such as coordination the coordination of the ester oxygen to nickel metal center, since ( , )-l-(methoxymethyl)-4-methyl-l,3-butadiene and (E,E)-1-(hydroxymethyl)-4-methyl-l,3-butadiene furnish the C4 adducts selectively together with the Cl adducts as minor products (not shown). Notably,... 

Methyl sorbate gives three dimeric products from sensitized irradiation, Eq. 52. The trans configuration of the reactant double bonds is retained in all of the products. 134> Over 80% of the product arises from... 

Examples of ditactic polydienes are provided by a class of crystalline polymers derived from the alkyl-esters of the trans-trans isomer of sorbic acid.101,102 For example trans-poly (methyl sorbate) (-CH(CH3)-CH =... 

This kind of conformational disorder has also been suggested for poly(methyl sorbate).105 It is therefore not unusual and also explains some properties of these polymers, as, for instance, the low entropy of melting.114... 

Table 14.3 Hydrogenation of methyl sorbate to 3-hexenoic acid methyl ester with [Cr(CO)3(arene)] (45) catalysts.

The authors extended their investigations to a series of functionalized dienes such as sorbic acid, methyl sorbate, 1-nitro-l,3-butadiene, and cyclic dienes. 

In contrast with the metal-free cycloaddition again, the efficiency of metal mediated cycloaddition reactions is relatively insensitive to the electronic nature of the reactants. This has been nicely demonstrated by Rigby and colleagues305 who treated complex 494 with a 1 1 mixture of methyl sorbate (502) and 1-trimethylsilyloxy-l,3-butadiene (50). The reaction proceeded in 90% yield and afforded 503 and 504 in a 46 54 ratio (equation 146). 

Nitrosyl cyanide, generated from nitrosyl chloride and silver cyanide in chloroform at — 20 °C, affords unstable products with various dienes, e.g. butadiene and 2,3-di-methyl-1,3-butadiene. With methyl sorbate, compound 182 is produced (equation 103), thebaine (183) gives 184 (equation 104)97 and 9,10-dimethylanthracene yields the stable cycloadduct 185, which decomposes into its components on heating and consequently can serve as a source of nitrosyl cyanide. Thus heating 185 with 1,4-diphenylbuta-1,3-diene gives the dihydrooxazine 186 and dimethylanthracene (equation 105)98. 

This work was repeated by several groups7 11 in the reaction of sodium dimethyl-malonate with methyl sorbate, Farmer and Metha9 observed small amounts of the 1,4-adduct besides the 1,6-addition product. Difficulties in conducting the transformations and analyzing the products are evident from reports on malonate additions to ethyl muconate12-14 depending on the reaction conditions, the expected 1,4-adduct (equation 4) or isomerization products formed by double bond displacement were isolated. Nucleophilic 1,4- and 1,6-addition reactions to 2,4-pentadienenitrile were also reported15-17. 

Michael additions to acceptor-substituted dienes are often followed by (spontaneous or induced) cyclizations. This was already noted by Vorlander and Groebel4 who obtained a substituted 1,3-cyclohexanedione by treatment of 6-phenyl-3,5-hexadien-2-one with diethyl malonate (equation 5). Obviously, the 1,4-addition product which is formed initially then undergoes cyclization, ester hydrolysis and decarboxylation. Similarly, reaction of methyl sorbate with methyl 4-nitrobutyrate gave the 1,6-adduct which was reductively cyclized to 6-methyl-l-azabicyclo[5.3.0]decane18 (equation 6). 

By far most of the reports on addition reactions of hetero-nucleophiles to activated dienes deal with sulfur-nucleophiles17,48,80,120-137, in particular in the synthesis of 7/3-sulfur-substituted steroids which, like their carbon-substituted counterparts (Section n.A), are of interest because of their ability to inhibit the biosynthesis of estrogens80,129-137. Early investigations17,120-122 concentrated on simple acyclic Michael acceptors like methyl sorbate and 2,4-pentadienenitrile. Bravo and coworkers120 observed the formation of a 3 1 mixture of the 1,6- and 1,4-adduct in the reaction of methyl sorbate with methanethiol in basic medium (equation 39). In contrast to this, 2,4-pentadienenitrile adds various thiols regioselectively at C-5, i.e. in a 1,6-fashion (equation 40)17,121,122, and the same is true for reactions of this substrate with hydrogen sulfide (equation 41), sodium bisulfite and ethyl thioglycolate17. 

Methyl sorbate reacts with dichlorocarbene in 22% yield at the less electron-deficient Y.S-unsaturated bond (Scheme 7.13) [31], as does methyl 3-(2,2,6-trimethylcyclohex-1 -enyl) propenoate (33%). 

Methyl sorbate and analogous monomers were polymerized in the presence of (/ )-2-methylbutyllithium or of complexes between butyllithium and optically active Lewis bases (329, 330) (see formulas 32 and 33) the polymers show weak optical activity. The prevailing configuration of the — CH(CH3)— group was determined by the sign of rotation of the methylsuccinic acid obtained from the polymer after ozonization. The low optical purity ( = 6%) found is related to the presence of a remarkable stereochemical disorder (115, 116) and to the fact that the chiral agent is active, at least in the case of methylbutyllithium, only in the initiation reaction. 

R and R groups and an all-trans arrangement of the double bonds. The polymer is named transerythrodiisotactic 1,4-poly (methyl sorbate) or diisotactic poly[eryr/tro-3-(methoxycar-bonyl)-4- -methylbut-1 -ene-1,4-diyl]. 

Styrene, leads to [4 + 2]-adducts exclusively (251-258) 242 is also isolated in varying amounts, With methyl sorbate both [4 + 2]- and [4 + 4]-adducts (259-262) are obtained. 1,4-Dicarbomethoxybutadiene does not add to 138 242 is obtained in 90% yield. All photoadducts (251-262) are photolabile on irradiation (z — 253.7 nm) they are reconverted to 138 and the alkene. Significantly for preparative purposes, the product distributions (stereo-, regio-, and peri-selectivity) differ considerably from those obtained in the thermal Diels-Alder reactions (Section IV,B) mechanistic details are given in the original papers. 

Natta carried out the anionic polymerization of methyl sorbate, a 1,3-diene, with an optically active initiator and obtained an optically active homopolymer with main-chain chirality. The high molecular weight crystalline polymer produced with (P)-2-methylbutyllithium had a tritactic (di-iso-rra/w-tactic) structure. This was probably the first metal-catalyzed asymmetric polymerization 134). Polymerization of other dienes was attempted by using various asymmetric methods 135). 

Amplification. See Chirality amplification Anhydrides, ring opening, 331 Anionic polymerization methyl sorbate, 174 trityl acrylate, 181 Annelation, Robinson method, 336 Antibiotics, 8, 44, 80 Antibodies, 12... 

Methyl-sorbate LiC4H (—) Menthyl-ethyl-ether... 

Table 2. Relationship between absolute configuration of the asymmetric carbon atoms present in the initiator or catalyst and absolute configuration of the asymmetric carbon atom of the methyl (or phenyl) succinic acid obtained by ozonolysis of poly-methyl-sorbate, poly-butyl-sorbate,... 

Poly-methyl-sorbate 2-methyl-butyl-lithium R s COOH 1 ch3-c-h... 

Poly-methyl-sorbate n-butyl-lithium-menthyl-ethyl-ether 1R, 3R, 4S R CHj-COOH COOH 1... 

Actually, levo rotatory methyl succinic acid and dextro rotatory methyl succinic acid were obtained by oxidation respectively from methyl sorbate and butyl sorbate polymers, obtained in the presence of (R)-2-methyl-butyl-lithium (36). 

Selective 1,4-hydrogenation of 1,3-dienes to (Z)-alkenes is possible with benzenechromium tricarbonyl as a catalyst precursor. Only those conjugated dienes that can adopt a cisoid conformation, and hence chelate to the metal, are hydrogenated. Methyl sorbate (68) is reduced to methyl (Z)-3-hexenoate (70) [46,47]. The reaction... 

Here the synthesis of a d(-19-methyl homolog of deserpidine (LII) has to be mentioned (194). For the initial Diels-Alder condensation, methyl sorbate was used instead of methyl vinylacrylate for the rest, this synthesis followed well-trodden paths. French workers have also... 

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