54655-07-1Relevant articles and documents
Radical-initiated polyolefinic cyclizations in linear triquinane synthesis. Model studies and total synthesis of (±)-hirsutene
Curran,Rakiewicz
, p. 3943 - 3958 (1985)
Details of a novel radical-initiated polyolefinic cyclization approach to linear condensed cyclopentanoids are reported. The strategy is executed in three stages: (1) S(n)2'-anti opening of a vinyl lactone to produce a trans-3,5-disubstituted cyclopentene, (2) rapid elaboration to a cyclization precursor, and (3) single step tandem radical cyclization to produce a cis-anti-cis tricyclo[3.3.0]undecane. Model substrates 16a and 16b give high yields of tricyclic products 17 and 18, respectively. An effort to rationalize the interesting endo selectivity via the Beckwith transition state model is proposed. Cyclizations of 28 and 29 to 30 and 31 demonstrate the viability of a tandem hexenyl-hexynyl cyclization. The work culminates with a total synthesis of (±)-hirsutene. A selective approach to methyl substituted vinyl lactones by Claisen rearrangement-phenylselenolactonization-elimination of acetoxy cyclopentenols is exemplified by the synthesis of 12. Tandem cyclization of 38 produces hirsutene (1) in a single step. Alternatively, cyclization of 37 yields trimethylsilyl hirsutene.
Formation of Alkynylgermyl-Substituted Germylenes via a Catenation of Ge Atoms
Liu, Chenghuan,Zhu, Keke,Han, Weichun,Liu, Xue,Zhang, Zheng-Feng,Su, Ming-Der,Wu, Di,Li, Yan
, p. 10123 - 10128 (2020)
Reactions of amidinate-stabilized germylene chlorides R1Ge(:)Cl (R1 = PhC(NtBu)2) and R2Ge(:)Cl (R2 = PhC(NCy)2, Cy = cyclohexanyl) with trimethylsilylethynyl lithium salt (LLi, L = a'C?f‰CTMS) afforded alkynylgermylsubstituted germylenes R1(:)Ge-GeL3 (1) and [R2GeL2]2Ge(:) (2), respectively. Both of them may undergo the formation of Gea'Ge single bonds with a concomitant 1,2-shift of ethynyl groups. DFT calculations determined the reaction pathways where two possible intermediates (:)GeL2 and RGe(:)L (R = R1, R2) are proposed, which were consistent with the trapping reactions of (:)GeL2 toward IAra(:)GeL2 (3, IAr = :C{N(Ar)CH}2, Ar = 2,6-iPr2C6H3). The reaction of 1 with N3TMS gave a new aminogermylene R1(:)Gea'N(TMS)-GeL3 (4), indicating a reactive Gea'Ge bond.
Pd-catalyzed sp-sp3cross-coupling of benzyl bromides using lithium acetylides
Buter, Jeffrey,Doze, Anna M.,Feringa, Ben L.,Mondal, Anirban,Visser, Paco
supporting information, p. 7529 - 7532 (2021/08/05)
Organolithium-based cross-coupling reactions have emerged as an indispensable method to construct C-C bonds. These transformations have proven particularly useful for the direct and fast coupling of various organolithium reagents (sp, sp2, and sp3) with aromatic (pseudo) halides (sp2). Here we present an efficient method for the cross-coupling of benzyl bromides (sp3) with lithium acetylides (sp). The reaction proceeds within 10 min at room temperature and can be performed in the presence of organolithium-sensitive functional groups such as esters, nitriles, amides and boronic esters. The potential application of the methodology is demonstrated in the preparation of key intermediates used in pharmaceuticals, chemical biology and natural products.
Intramolecular Pd-Catalyzed Formal anti-Carboalkoxylation of Alkynes: Access to Tetrasubstituted Enol Ethers
Schitter, Theresa,Jones, Peter G.,Werz, Daniel B.
supporting information, p. 13446 - 13449 (2018/09/21)
An intramolecular Pd-catalyzed formal anti-carboalkoxylation reaction is presented that provides access to tetrasubstituted enol ethers. The key to success is a cascade consisting of a formal anti-carbopalladation of a carbon–carbon triple bond followed by a nucleophilic attack of a hydroxy group at the emerging vinyl organopalladium species. The desired transformation proceeded smoothly with primary, secondary, and tertiary alcohols, and even with phenols. Depending on the substitution pattern of the enol ethers, a further Tsuji–Trost-type step may occur resulting in oligocyclic ketals.
