Propenylidenes

The linear dimerization of substituted conjugated dienes is difficult, but the Pd-catalyzed intramolecular dimerization reaction of the 1,3,9,11-tetraene 13 gives the 3-propenylidene-4-allylpiperidine derivative 14, which has the 1,3,7-octatriene system. The corresponding 1,3,8,10-tetraene also affords the 3-pro-penylindene-4-allylcyclopentane derivative[18]. 

Development of (Z, )-5-(2-methyl-3-phenyl-2-propenylidene)4-oxo-2-thio-xothiazolidine-3-acetic acid (Epalrestat, Kinedak), an aldose reductase inhibitor 97YGK651. 

Several trialkoxy(2-butenyl)zirconium(IV)6,7i 18 and 2-butenylbis(cyclopentadienyl)zirco-nium(IV)18,19 124 complexes have been investigated with respect to the diastereoselectivity on addition to aldehydes. Chlorobis(cyclopentadienyl)-(3-tributylstannyl-2-propenyl)zirconium(IV), prepared by hydrozirconation of tributyl-(l,2-propadienyl)tin, accomplishes the (E)-selective, Wittig-like 1,2-propenylidenation of aldehydes and methyl ketones125. 

It has been shown by Schulz and Kern2 J that the radical polymerization of acrolein can take the course of the 1,2-mechanism as well as that of the 1,4- or 3,4-mechanism leading to formylethylene, oxy-2-propenylene, or oxy-2-propenylidene units, respectively. This behaviour of acrolein and its derivatives seems to be also retained to a certain extent, in the radical copolymerization of 4 with AN causing a decrease fo the content of aldehyde groups in the copolymers. 

The formation of the tricarbonylchromium-complexed fulvene 81 from the 3-dimethylamino-3-(2 -trimethylsilyloxy-2 -propyl)propenylidene complex 80 and 1-pentyne also constitutes a formal [3+2] cycloaddition, although the mechanism is still obscure (Scheme 17) [76]. The rf-complex 81 must arise after an initial alkyne insertion, followed by cyclization, 1,2-shift of the dimethylamino group, and subsequent elimination of the trimethylsilyloxy moiety. Particularly conspicuous here are the alkyne insertion with opposite regioselectivity as compared to that in the Dotz reaction, and the migration of the dimethylamino functionality, which must occur by an intra- or intermo-lecular process. The mode of formation of the cyclopenta[Z ]pyran by-product 82 will be discussed in the next section. 

Scheme 17 Formation of the (tricarbonylchromium)-complexed fulvene 81 and the cyclo-penta[b]pyran 82 from the 3-dimethylamino-3-(2 -trimethylsilyloxy-2 -propyl)propenylidene complex 80 and 1-pentyne [76]...

Because of its carbene functionality, our decision to consider only the parent hydrocarbons would mean that cyclopropenylidene would be ignored here even if monoolefins were of relevance. This philosophy accounts for our ignoring the energetics of the isomeric carbenes, propargylene (HCCCH) and propenylidene (CH2CC), in the earlier section on cumulenes in the current chapter. 

Our interest in carbenes is closely related to our work on conjugated hydrocarbons containing four electrons. The parent molecules of three completely different families within this category are 1,3-cyclobutadiene (1), cyclo-propenylidene (2), and trimethylenemethane (3). 

Benzoylation of D-g/ycero-D-gw/o-heptono-1,4-lactone with an excess of benzoyl chloride and pyridine afforded the hept-2-enono-1,4-lactone as the main product (198). The di- and triunsaturated compounds were isolated in very low yield from the mother liquors (199). Higher yields of the di- and triunsaturated derivatives 153 and 154 were obtained when the /5-elimination reaction was performed with triethylamine on the previously synthesized per-O-benzoyl D-g/ycero-D-gw/o-heptono-1,4-lactone. Employing 10% triethylamine in chloroform, the lactone 153 was obtained as an E, Z dias-tereomeric mixture in 9 11 ratio as determined by H n.m.r. When 20% triethylamine was used, the furanone 154 was obtained in 59% yield (200). Its structure was assigned, on the basis of H and 13C n.m.r. spectra, as 3 -benzoyloxy - (5Z)-[(Z)-3 - benzoyloxy - 2 - propenyliden] -2(5 H)- furanone. The stereochemistry of the exocyclic double bonds was established (201) by nuclear Overhauser effect spectroscopy (NOESY). 

Early investigations dealing with the synthesis and reactions of tri- and tetra-amino-substituted allenes were performed by Gompper and co-workers [151]. Scheme 8.70 illustrates a typical method for the preparation of 261 by deprotonation of propenylidene ammonium salt 260. However, this chemistry has not been developed further during the last three decades. 

Fig. 7 Structures of the dyes forming aggregates on DNA (a) l-methyI-4-[[3-methyl-2(3//)-benzothiazolylidene]methyl]-quinolinium (Thiazole Orange, TO), (b) 3,3 -diethyIthiadicarbo-cyanine (DiSC2(5)), (c) 3,3 -trimethylammoniopropylthiadicarbocyanine (DiSC3+(5)), (d) 2- [(Z)-2-(2,5-dihydro-2-thienyl)-3 - [3 -methyl-2(3/f)-benzothiazolylidene] -1 -propenyl] -3 -methyl -benzothiazol-3-ium (L-21), (e) 2-[( )-3-[3,7-diethyT6-[( ,2 )-3-(l-ethyl-3,3-dimethyl-3/7-indo-lium-2-yl)-2-propenylidene]-6,7-dihydrothiazolo[5,4-/]benzothiazol-2(3//)-ylidene]-l-propenyl]-l-ethyl-3,3-dimethyl-3//-indolium (BCD), (f) 3-methyl-2-[( )-3-methyl-2-[[3-methyl-2(3/f)-ben-zothiazolylidene]methyl]-l-butenyl]-benzothiazol-3-ium (Cyan ]3iPr)...

Dichloro(3,3-diphenyl-2-propenylidene)-6 s-(triphenylphosphine)-ruthenium (compound 22) ... 

Potassium methyl dicyanoacetate 359 reacted smoothly with (3,3-dichloro-2-propenylidene)dimethylammonium chloride 360 in chloroform at room temperature to yield a 1 1 mixture of the ( )- and (Z)-isomers of the zwitterionic 1,3-oxazine iminium salts 113Aand 113B (Equation 38) <1999H(51)2893>. 

Monomethylacryloyl and vinylbenzyl derivatives of sucrose have been prepared as intermediates for polymers, and preparation of a range of copolymers of styrene and O-methylacryloylsucrose has been described (114). Synthesis of 4- and 6-O-acryloylsucrose has been achieved by acid-catalyzed hydrolysis of 4,6-0-(l-ethoxy-2-propenylidene)sucrose (76). These acryloyl derivatives have been polymerized and copolymerized with styrene (qv). 

Vlalondioate Dimethyl 3.3.3-Trifluoro-2-irifluoroniethyl-1-propenyliden- ElOb,. 353 (— HF - En)... 

Malondinate Dimethyl (2-Trifluoro-methyl-1 -propenyliden)- El0h2, 99 (— H F -> En)... 

Malondioate Diethyl (Trifluoro-2-trifluormethy]-l -propenyliden)-E10b2, 51 (Educt)... 

The 2-propenylidene acetals of hexopyranosides, such as 3, are selectively reduced by acidic sodium cyanoborohydride to 6-0-2-propenyl ethers (eg., 4).3... 

An example of the simplicity and potential of the photo-oxygenation reaction is described for the preparation of (Z)-l-hydroperoxy-A-[(Z)-3-methoxycarbonyl)-2-propenylidene]cyclohexylamine A-oxide (P) starting from 2-methoxyfuran and cyclohexanone oxime, which both can be purchased and used without further purification. 

QIIkjOa, 5018-30-4) see Sulfadoxine [2,S -(2a,5a,6(i) -3,3-dimethyl-6-methoxy-7-oxo-6-[[3-oxo-3-phenoxy-2-(3-thicnyl)-l-propenylidene]amino]-4-thia-l-azabicyclo[3.2.0]heptane-2-carboxylic acid (4-nitrophe-nylimethyl ester (C1(iH22,NjO,S2) see Temocillin... 

The ruthenacyclopentene intermediate can also undergo insertion of ethylene to give a ruthenacycloheptene. Subsequent unexpectedly observed /1-hydride elimination occurred and led then to cyclization products with a propenylidene substituent [79] (Eq. 58). Various enynes.with substituents on triple or double bonds, have been cyclized to form carbocyclic and heterocyclic compounds in good yields. 

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