21003-54-3Relevant academic research and scientific papers
Transition metal-free diastereospecific synthesis of (Z)-2-arylidene-2,3-dihydrobenzo[b][1,4]dioxines by reaction of (Z)-1,2-dibromo-3-aryl-2-propenes with catechols
Beifuss, Uwe,Bharatam, Prasad V.,Conrad, Jürgen,Frey, Wolfgang,Rekowski, Szymon P.,Wani, Aabid A.
, (2020/09/18)
A transition metal-free, diastereospecific reaction between substituted (Z)-1,2-dibromo-3-phenyl-2-propenes and substituted catechols using Cs2CO3 as a base at 140 °C for 18 h delivers exclusively substituted (Z)-2-arylidene-2,3-dihy
Hydrodebromination of allylic and benzylic bromides with water catalyzed by a rhodium porphyrin complex
Yang, Wu,Chen, Chen,Chan, Kin Shing
, p. 12879 - 12883 (2018/10/02)
Hydrodebromination of allylic and benzylic bromides was successfully achieved by a rhodium porphyrin complex catalyst using water as the hydrogen source without a sacrificial reductant. Mechanistic investigations suggest that bromine atom abstraction via a rhodium porphyrin metalloradical operates to give the rhodium porphyrin alkyl species and the subsequent hydrolysis of the rhodium porphyrin alkyl species to a hydrocarbon product is a key step to harness the hydrogen from water.
Titanocene(III) chloride mediated radical induced addition-elimination route to the synthesis of racemic and optically active trisubstituted tetrahydrofurans: Formal synthesis of magnofargesin and 7’-epimagnofargesin
Chakraborty,Mandal,Roy
, p. 1067 - 1079 (2016/07/19)
Titanocene(III) Chloride mediated radical induced synthesis of 4-benzylidene substituted tetrahydrofuran, a typical lignan skeleton, has been accomplished in good yield through addition-elimination route in racemic as well as in optically active forms. The method has been applied to the synthesis of furano lignans, magnofargesin (1) and 7’-epimagnofargesin (2) in optically active forms.
Selectfluor-mediated mild oxidative halogenation and thiocyanation of 1-aryl-allenes with TMSX (X = Cl, Br, I, NCS) and NH4SCN
Laali, Kenneth K.,Nandi, Ganesh C.,Bunge, Scott D.
supporting information, p. 2401 - 2405 (2014/05/06)
Presence of TMSX (X = Cl, Br, I) unleashes the oxidative character of Selectfluor and provides a mild dihalogenation method for 1-arylallenes. Preference for 2,3-addition was observed with TMSCl in MeCN irrespective of the nature of the substituent on the aryl moiety, whereas 1,2-addition was preferred in [BMIM][BF4]. With TMSBr and TMSI only products corresponding to 2,3-addition were observed. Reactions carried out with TMSBr in IL solvents gave the corresponding monobromoalkenes as a major product along with the isomeric dibromo-alkenes. Reaction with NH4SCN provided convenient access to dithiocyanate derivatives. The same products were formed via TMS-NCS/Selectfluor. Formation of common products via TMSNCS and NH 4SCN points to the formation and interplay of SCN+/ NCS+ as incipient electrophiles.
Copper-free asymmetric allylic alkylation using grignard reagents on bifunctional allylic bromides
Grassi, David,Alexakis, Alexandre
supporting information; experimental part, p. 1568 - 1571 (2012/06/01)
A series of substrates containing a vinylic bromide were employed in a copper-free methodology using bidendate NHC ligands. The desired compounds are generally obtained with good enantioselectivity and good regioselectivity. Importantly the copper-catalyzed system afforded a lower enantioselectivity value. The catalytic products could be transformed into a broad scope of new 1,1-disubstituted olefins in a single step transformation without erosion of the enantioselectivity.
Catalytic asymmetric claisen rearrangement of enolphosphonates: Construction of vicinal tertiary and all-carbon quaternary centers
Tan, Jiajing,Cheon, Cheol-Hong,Yamamoto, Hisashi
supporting information; experimental part, p. 8264 - 8267 (2012/09/08)
A copper-catalyzed enantioselective Claisen rearrangement of easily accessible enolphosphonates using the commercially available PhBOX as the chiral ligand was developed. A wide range of rearrangement products with contiguous tertiary and all-carbon quaternary centers were obtained in excellent yields and stereoselectivities. The α-ketophosphonate substituent in the products could be easily transformed into other functional groups. Copyright
Efficient ring-closing metathesis of alkenyl bromides: The importance of protecting the catalyst during the olefin approach
Gatti, Michele,Drinkel, Emma,Wu, Linglin,Pusterla, Ivano,Gaggia, Fiona,Dorta, Reto
supporting information; experimental part, p. 15179 - 15181 (2010/12/24)
We present the first productive ring-closing metathesis reaction that leads to the construction of cyclic alkenyl bromides. Efficient catalysis employing commercially available Grubbs II catalyst is possible through appropriate modification of the starting bromoalkene moiety.
Conversion of bromoalkenes into alkynes by wet tetra-n-butylammonium fluoride
Okutani, Masaru,Mori, Yuji
supporting information; experimental part, p. 442 - 444 (2009/04/10)
(Chemical Equation Presented) Tetra-n-butylammonium fluoride was found to be a mild and efficient base for the elimination reaction of bromoalkenes. Treatment of 1,1-dibromoalkenes, (Z)-1-bromoalkenes, and internal bromoalkenes with 5 equiv of TBAF·3H2O in DMF yielded terminal and internal alkynes in high yields without undue regard to the presence of water.
Cascade radical synthesis of heteroarenes via iminyl radicals
Bowman,Bridge,Brookes,Cloonan,Leach
, p. 58 - 68 (2007/10/03)
A novel cascade cyclisation protocol has been developed which 'zips up' two rings to form new tetracycles. In the protocol, treatment of vinyl bromides and iodides with hexamethylditin (Me3Sn· yields intermediate vinyl radicals which undergo 5-exo cyclisation onto nitrile groups to yield intermediate iminyl radicals. The iminyl radicals can undergo 6-endo cyclisation (or 5-exo followed by neophyl rearrangement) to yield tetracyclic π-radicals which lose hydrogen (H·) in an H-abstraction step. Methyl radicals, generated from the breakdown of trimethylstannyl radicals (Me3Sn·), are proposed as a possible H-abstractor for this final oxidative step. The protocol has been used to synthesise the tetracyclic rings A-D (tetracycle indolizino[1,2-b]quinolin-9(11H)-one) of the anticancer alkaloids camptothecin, mappicine, nothapodytine B and nothapodytine A. The protocol has also been applied to the synthesis of analogues of camptothecin in which ring A has been replaced by thiophene (8,10-dihydrothieno[2′,3′:5,6]pyrido[2,3-a]indolizin-8-one) and ring D by pyrrole (10H-pyrrolizino[1,2-b]quinoline) and benzene (11H-indeno[1,2-b]quinolin-11-one).
Synthesis of heteroarenes via radical cyclisation onto nitriles
Bowman,Bridge,Cloonan,Leach
, p. 765 - 768 (2007/10/03)
A new protocol for the synthesis of tetracyclic nitrogen heteroarenes using cascade radical cyclisation has been developed. The key steps involve 5-exo vinyl radical cyclisation onto nitriles to yield intermediate iminyl radicals which cyclise onto an arene rings. Rings A-D of the anticancer alkaloids camptothecin, mappicine and nothapodytines A and B have been synthesised using this protocol.
