Acetylenedicarboxylates reactions with carbenes

Carbonyl compounds and imines are the electrophilic partner of isocyanides in the Passerini-3CR and the Ugi-4CR, respectively. Other highly electrophilic multiple bonds, such as in dimethyl acetylenedicarboxylate (DMAD), are also known to react with isocyanides. The initially formed 1 1 zwitterionic species having carbanion, carbene character can undergo further reaction with DMAD and isocyanides in different molar ratios, leading to a variety of heterocyclic systems (Scheme 5.32) [69]. 

PhCH2) catalyze the benzoin condensation. The methyl derivative (303 R = Me) readily cleaves to yield the nucleophilic carbene (304), which has been trapped by reaction with carbon disulphide to yield the cross-conjugated 1,3-dipole (305) the latter in turn adds dimethyl acetylenedicarboxylate to form the dithiole (306).286... 

Reaction of carbene, generated from PhHgCBrjF, with benzaldehyde and dimethyl acetylenedicarboxylate afforded 2-bromo-2-fluoro-2,3-dihydrofuran 63. The compound 63 was aromatized by treatment with sodium methoxide producing fluorofuran 64. The reaction proceeded via intermediate carbonyl yUde that was trapped with dimethyl acetylenedicarboxylate in the subsequent [3+2] cycloaddition reaction [45]. 

In contrast to the reaction of an i72-CS2-rhodium complex with dimethyl acetylenedicarboxylate which gives rise to a metallocycle,186 the iron complexes 103 are converted by activated acetylenes into air-sensitive carbene complexes 104. Decomposition of the latter in air provides an unusual synthetic route to substituted tetrathiofulvene derivatives (Scheme 121).187... 

Thermal decomposition of the diazo compounds 116a,b in methanol or ethanol, in the presence of Cu(acac)2 as catalyst, resulted in an intramolecular carbene reaction the benzo[c]furans 117a,b were not isolated, but 117b could be trapped with A-phenylmaleimide and dimethyl acetylenedicarboxylate, to give compounds 118 (endo exo =1 1, 90%) and 121 (92%). Dimethyl fumarate yielded adduct 119 (15%) and supposedly 120 (83%) concerning this structure the same objections can be raised as in the case of... 

When the diazoesters (240) and (241) were thermally decomposed in the presence of copper(II) acetoacetate ester as catalyst, an intermolecular carbene reaction occurred, the resulting benzo[c]furans (242) and (243) were not isolated but were trapped as the Diels-Alder adducts with N- methylmaleimide and dimethyl acetylenedicarboxylate (76CL287). 

Phosphinidenes (R-P), short-lived, reactive intermediates that are isoelec-tronic with nitrenes and carbenes, are accessible by fragmentation of phos-phiranes, phosphol-3-enes, triazaphospholenes, and oxazaphospholenes and can be characterized by trapping reactions. The metal-complexed species [R-P-M, e.g., M = W(CO)5] are more stable (but also not isolable) and react more selectively. As a model example we describe the transformation of (3,4-dimethyl-l-phenylphosphole)(pentacarbonyl)tungsten 4 with dimethyl acetylenedicarboxylate to the 7-phosphanorbomadiene derivative 5.11 The (phosphinidene)(pentacarbonyl)tungsten complex 6 is generated from the latter by a [4+ 1]-cycloreversion and trapped with diphenylacetylene via a [2+1]-cycloaddition to furnish the triphenyl-2-phosphirene complex 7 (Scheme l).12... 

A zwitterion approach is used to functionalize Dy Cs2. It shows both high selectivity and efficiency [161], Treatment of Dy C2v-Cs2 with dimethyl acetylenedicarboxylate (DMAD) and triphenylphosphine gave rise to one mono-adduct with a yield of up to 90%. Structural analysis of the adduct confirmed an open-cage structure, and the addition sites are the same as those found previously for the carbene derivative of La Cs2(Ad), which accordingly leaves an open question about the reaction mechanism. 

A variety of cyclic phosphonium ylide structures have been reported. Hetero-cyclic and -bicyclic structures, including the ylide (11) and a variety of iminophosphoranes, are the products of the reaction of the 1,2-dihydro-1,3,2-diazaphosphinine (10) with dimethyl acetylenedicarboxylate. Attempts to prepare a simple adduct of DBN with the (phosphino)(P-chlorophosphonio) carbene (12) led instead to formation of the unsaturated tricyclic adduct (13). The diphosphete structure (14) is the product of a simple two component reaction of dichloro(bis(trimethylsilyl)methylphosphine) with DBU. Details of the synthesis, chemistry and structure of X -phosphetes (15), benzo-X, -phosphetes (16), and naphtho-X -phosphetes (17) have been reported. 2,4-Diphosphoniodihydro-phosphetide cations (19) have been prepared by condensation of the... 

R" = COOMe to 22 dm mol s" for R = H and R" = Ph. The rate constants for addition of PhCF were slightly lower. The rate constants decreased with increasing Ti-ionization potential of the alkyne, except for very electron-deficient alkynes such as dimethyl acetylenedicarboxylate. The correlation indicated that in these additions the carbenes generally behave as electrophiles, whereas with the acetylenedicarboxylate carbenic nu-cleophilicity comes into play. The rate constant of addition of phenylchlorocarbene to 3-hexyne was determined as a function of temperature. The reaction appeared to be entropy controlled Ea = 8.8 + 0.4 kJ mol and AS = -82 J mol" K The corresponding alkenes have rate constants and activation parameters in the same order of magnitude. 

Attempts to trap with dimethyl acetylenedicarboxylate (DMAD) a presumed intermediate ylide formed upon rhodium-catalyzed carbene generation led instead to a 33% yield of oxazocine (74), apparently formed by fragmentation of the initial [3 -I- 2] cycloadduct of DMAD with the ylide, followed by acyl migration (Scheme 27). Ylide tautomerization, followed by an analogous sequence of reactions, accounts for a 24% yield of isomer (95) <92TL3273>. 

H.-R. Pan, X.-R. Wang, C.-X. Yan, Z.-X. Sun, Y. Cheng, Org. Biomol. Chem. 2011, 9, 2166—2174. The multicomponent reaction of imidazo[l,5-a]pyridine carbenes with phthalal-dehydes and dimethyl acetylenedicarboxylate a facile construction of benzo[d]furo[3,2-h]azepines. 

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