Ethyl 2,3-butadienoate

In the presence of triphenylphosphine as a catalyst, benzotriazole adds readily to activated allenes. Its reaction with ethyl 2,3-butadienoate produces a mixture of adducts 149 (54%) and 150 (20%). Both derivatives form exclusively as (Tyi-isomers <2006T3710>. In a reaction of benzotriazole with dibenzoylacetylene and... 

Sodium salt of diethyl acetamidomalonate 480 reacts with ethyl 2,3-butadienoate in the presence of a catalytic amount of EtONa to afford /fy-unsaturated enoate 481, which can be easily decarboxylated leading to /3-methyleneglutamic acid hydrochloride 482 [220],... 

In 1954, Eglinton et al. [235] reported the reaction of ethyl 2,3-butadienoate with NaOEt in EtOH. It was observed that the product is ethyl 2-ethoxy-2-butenoate, showing that the C=C bond migrated from the /3,/-position to the a,/3-position under the basic conditions [235],... 

Cydoaddition reactions of electron-deficient allenes are also known. In the presence of A1C13, ethyl 2,3-butadienoate (32) reacts with alkenes to give cyclobutyl-ideneacetic esters at room temperature [28]. 

A fundamentally different approach to the synthesis of 3-pyrrolines is evidenced in the annulation in Eq. 13.50 [58]. Ethyl 2,3-butadienoate 150 reacts with N-sulfony-limine 151 in the presence of triphenylphosphine under very mild conditions to give JV-protected 3-pyrroline 152 in 90% yield. The mechanism that has been postulated is related to that of the Baylis-Hillman reaction. Michael addition of triphenylphosphine to the allenyl ester generates a zwitterion that combines with the imine to give 153 in a non-concerted process. This is followed by ring closure, proton exchange and expulsion of triphenylphosphine to give 152. This annulation is successful only for aromatic or cinnamyl imines [59]. 

Phosphine-Catalyzed Reactions. This ligand has also been shown to be effective in the direct organocatalysis of asymmetric processes. For example, the phosphine-catalyzed [3 -1- 2] annula-tion reaction of ethyl 2,3-butadienoate and isobutyl acrylate produces two cyclopentene regioisomers (1 and 2) (eq 2). Isomer 1 generally predominates and enantiomeric excesses ranging from... 

Dicarbonylation occurs mainly by the carbonylation of propargylic halides and alcohols carried out under a high pressure of carbon monoxide. The carbonylation of propargyl bromide (51) at 20 atm affords 2,3-butadienoate (52) as described in Section 11.3.2.2. On the other hand, carbonylation of propargyl chloride (77) in methanol at room temperature under high pressure (100 atm) catalyzed by PdClj or Pd/charcoal afforded dimethyl itaconate (79). The primary product seems to be 2,3-butadienoate (78), which is carbonylated further (Scheme 11-23) [10,11]. As supporting evidence, formation of diethyl itaconate (81) in 64% yield by the carbonylation of ethyl 2,3-butadienoate (80) at room temperature under high pressure was confiimed. 

Adducts of diorganozinc reagents with ethyl 2,3-butadienoate also show diene character toward the carbonyl group. The hetero-Diels - Alder reaction is asymmetrized in the presence of Cu(OAc)2 and DIFLUORPHOS. ... 

The condensation of benzyl cyclopropyl ketones with ethyl 2,3-butadienoate is interesting. The furocoumarin system is elaborated. ... 

The normal aza-MBH adducts 40 could be formed in moderate yields in the PPhs-catalyzed reaction between methyl 2,3-butadienoate and A -(ethoxy-carbonyl)benzaldimine, while only trace normal aza-MBH adducts 41 were afforded for DABCO-catalyzed reactions of A-tosylated imines with ethyl 2,3-butadienoate (Scheme 1.19). These results show that the reactivities of both imines and catalysts influence the final products using the same starting materials. 

Recently, we reported the different reactivity patterns shown by nitrogen- and phosphorus-containing Lewis bases as catalysts in the reactions of A-Boc-imines 42 with ethyl 2,3-butadienoate - they differ from the previous observations in the normal aza-MBH reactions of other imines and are beyond the scope of the aza-MBH reactions." The normal aza-MBH products 43 were obtained in good to excellent yields with DABCO as catalyst, whereas novel rearrangement product 44 could be formed in moderate yields by using PPhs as catalyst (Scheme 1.20). 

The phosphane catalyzed [3+2] cycloaddition between aUenoates and activated alkenes have attracted extensive attention since its discovery [95, 96]. Recently, in 2009, Krische and his co-worker reported a phosphane-catalyzed [3+2] cycloaddition of ethyl-2,3-butadienoate 237 with an enone 238 to give the cis-fused cyclopenta[c]pyran 239. They applied this methodology to the total synthesis of the iridoid p-glucoside (+)-geniposide 240, Scheme 3.77 [97], Alternatively, phosphane-catalyzed [3+2] annulation of aUenoates with aldehydes, affording 2-alky-lidenetetrahydrofurans, was reported by He and his co-workers [98]. 

M -BuLi in hexane added with stirring to a soln. of ethyl 2,3-butadienoate in THF at — 105°, after 1 h the mixture treated dropwise with a soln. of propanal, and stirring continued at —105° to —99° for 5 h ethyl 3-hydroxy-2-vinylidenepen-tanoate. Y 57.8%. F.e. and with DABCO s. S. Tsuboi et al., Chem. Letters 1988, 2003-4. 

P(p-FC6H4)3-catalyzed tandem reaction between ethyl-2,3-butadienoate and nitroalkenes leads to substituted cyclopentenes (Scheme 6.6). The reaction involves a [3-f2] cycloaddition and a subsequent umpolung addition. The asymmetric version of this tandem reaction can be achieved by using chiral phosphine, that is, (/ )-2,2 -bis(diphenylphosphino)-1,1 -binaphthyl (Binap) [8],... 

---