851758-56-0Relevant academic research and scientific papers
Synthetic and mechanistic investigations on the rearrangement of 2,3-unsaturated 1,4-bis(alkylidene)carbenes to enediynes
Sahu, Bichismita,Muruganantham, Rajendran,Namboothiri, Irishi N. N.
, p. 2477 - 2489 (2007)
The synthesis of 3,4-ene-1,5-diynes, the key structural moiety present in several naturally occurring antitumor antibiotics, from 1,2-enedialdehydes under two different experimental conditions is reported. One method involves the dibromomethylenation of dialdehydes under Corey-Fuchs conditions (CBr 4, Ph3P, and Zn) and treatment of the resulting tetrabromides with nBuLi or LDA to afford enediynes. The second method involves a base-mediated reaction of enedialdehydes with diethyl (1-diazo-2-oxopropyl) phosphonate (Bestmann-Ohira reagent) and subsequent transformation of the bis(diazo) compounds generated in situ to enediynes. While the transformation of bis(diazo) compounds to enediynes could take place exclusively through alkylidene-carbenes, generated in situ by geminal elimination of N2, an alternative pathway, involving the vicinal elimination of HBr to afford an intermediate bromoalkyne and its subsequent metal-halogen exchange and protonation during workup, exists for the bis(dibromoalkylidenes). However, our deuterium-labeling experiments with a model substrate, deuterated p-methoxybenzylidene dibromide, established the predominance of the alkylidenecarbenes, generated in situ by metal-halogen exchange and elimination, for this substrate and, by analogy, for the tetrabromides as well. The scope of this novel methodology was extended to the synthesis of various heteroatom-based (S, Se, and P) enediynes by quenching the acetylides with suitable electrophiles. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
A highly selective catalytic system for the cross-coupling of (E)-Styryl Bromide with Benzeneboronic acid: Application to the synthesisof all-trans poly(arylenevinylene)s
Wakioka, Masayuki,Mutoh, Yuichiro,Takita, Ryo,Ozawa, Fumiyuki
supporting information; experimental part, p. 1292 - 1298 (2010/01/30)
Ahighlyselective system for palladium-catalyzed polycondensation of (E, E)-1,4-bis(2-bromoethenyl)benzene ((E, E)-1)with 2,5-dioctyloxybenzene-1,4- diboronicacid(2a)togive all-trans poly[(p-phenylenevinylene)-alt-(2,5- dioctyloxy-1,4-phenylenevinylene)] (all-trans 3) has been investigated using (E)-styryl bromide ((E)-4) and 2,5-dioctyl- oxybenzeneboronicacid(5a) as model compounds of and 2a, respectively. The reaction of (E)-4 and 5a in toluene in the presence of Pd(PPh3)4 catalyst and aqueous K 2CO3 base affords considerable amounts of homocoupling products (i.e., 1,4-diphenylbutadiene (13%) and 2,2',5,5'-tetraoctyloxybiphenyl (22%)), together with (E)-2,5-dioctyl- oxystilbene ((E)-6a) as the cross-coupling product (30%). The use of aqueous NaOH as a strong base and Bu4NBr as a phase-transfer catalyst notably reduces the homocoupling products, and the use of Pd(PBut3)2 instead of Pd(PPh3)4 results inalmost perfect selectivity of the cross-coupling product (E)-6a. Under optimized catalytic conditions, the desired all- trans 3 has been successfully prepared without notabledefects in the polymer chain.
3H-benzophosphepine complexes: Versatile phosphinidene precursors
Borst, Mark L. G.,Bulo, Rosa E.,Gibney, Daniele J.,Alem, Yonathan,De Kanter, Frans J. J.,Ehlers, Andreas W.,Schakel, Marius,Lutz, Martin,Spek, Anthony L.,Lammertsma, Koop
, p. 16985 - 16999 (2007/10/03)
The synthesis of a variety of benzophosphepine complexes [R = Ph, t-Bu, Me; MLn = W(CO)5, Mo(CO)5, Cr(CO)5, Mn(CO)2Cp] by two successive hydrophosphinations of 1,2-diethynylbenzene is discussed in det
Synthesis of arenediynes via the vinylidenecarbene-acetylene rearrangement
Sahu, Bichismita,Namboothiri, Irishi N.N.,Persky, Rachel
, p. 2593 - 2597 (2007/10/03)
A convenient method for the two-step synthesis of arenediynes from 1,2-arenedialdehydes is reported. Dibromomethylenation of dialdehydes under Corey-Fuchs conditions (CBr4, Ph3P, Zn) provides the tetrabromides in excellent yields. Treatment of the tetrabromides with n-BuLi or LDA affords 3,4-unsaturated 1,5-diynes, the key structural moiety present in several naturally occurring antitumour antibiotics, in varying yields. The key intermediates in these transformations appear to be vinylidenecarbenes or carbenoids, generated in situ via metal-halogen exchange and elimination.
