Let M be a 3-manifold, F= ／{F1,F2,／…,Fn} be a collection of essential closed surfaces in M （for any i,j ∈ {1,...,n}, if i≠j, Fi is not parallel to Fj and Fi∩ Fj=Ф） and 0M be a collection of components of ...Let M be a 3-manifold, F= ／{F1,F2,／…,Fn} be a collection of essential closed surfaces in M （for any i,j ∈ {1,...,n}, if i≠j, Fi is not parallel to Fj and Fi∩ Fj=Ф） and 0M be a collection of components of M. Suppose M- ∪Fi∈F Fi×（-1,1） contains k components M1,M2…,Mk. If each Mi has a Heegaard splitting Vi ∪Si Wi with d（Si） 〉 4（g（M1）＋ … ＋g（Mk））, then any minimal Heegaard splitting of M relative to 0M is obtained by doing amalgamations and self-amalgamations from minimal Heegaard splittings or -stabilization of minimal Heegaard splittings of M1,M2…,Mk.展开更多
Transition metal-catalyzed allylic substitution is a key reaction for forming carbon-carbon and carbon-heteroatom bonds,with broad applications in organic synthesis.While most methods rely on“soft”stabilized nucleop...Transition metal-catalyzed allylic substitution is a key reaction for forming carbon-carbon and carbon-heteroatom bonds,with broad applications in organic synthesis.While most methods rely on“soft”stabilized nucleophiles,the use of“hard”unstabilized derivatives has been less explored due to their high reactivity and challenges associated with controlling regio-and stereoselectivity.This review highlights advances in catalytic allylic substitution with unstabilized organometallic nucleophiles,focusing on aryl,alkyl,allyl,alkenyl,alkynyl,benzyl,and allenyl reagents and their direct cross-coupling with acyclic and cyclic allylic substrates.Key developments are categorized by reaction type,including achiral,racemic,stereoselective,and stereospecific processes.These advancements provide deeper insight into the reaction progress,challenges,and limitations.We anticipate a better understanding of the underlying mechanistic intricacies will further broaden their applicability in target-directed synthesis.展开更多
基金Supported by the National Natural Science Foundation of China(Grant No.10901029)
文摘Let M be a 3-manifold, F= ／{F1,F2,／…,Fn} be a collection of essential closed surfaces in M （for any i,j ∈ {1,...,n}, if i≠j, Fi is not parallel to Fj and Fi∩ Fj=Ф） and 0M be a collection of components of M. Suppose M- ∪Fi∈F Fi×（-1,1） contains k components M1,M2…,Mk. If each Mi has a Heegaard splitting Vi ∪Si Wi with d（Si） 〉 4（g（M1）＋ … ＋g（Mk））, then any minimal Heegaard splitting of M relative to 0M is obtained by doing amalgamations and self-amalgamations from minimal Heegaard splittings or -stabilization of minimal Heegaard splittings of M1,M2…,Mk.
基金supported by the Natural Sciences and Engineering Research Council of Canada(NSERC)through a Discovery Grant and a Tier 1 Canada Research Chair(P.A.E)the Huxiang High-Level Talent Gathering Project from the Science and Technology Department of Hunan Province(2020RC5001)。
文摘Transition metal-catalyzed allylic substitution is a key reaction for forming carbon-carbon and carbon-heteroatom bonds,with broad applications in organic synthesis.While most methods rely on“soft”stabilized nucleophiles,the use of“hard”unstabilized derivatives has been less explored due to their high reactivity and challenges associated with controlling regio-and stereoselectivity.This review highlights advances in catalytic allylic substitution with unstabilized organometallic nucleophiles,focusing on aryl,alkyl,allyl,alkenyl,alkynyl,benzyl,and allenyl reagents and their direct cross-coupling with acyclic and cyclic allylic substrates.Key developments are categorized by reaction type,including achiral,racemic,stereoselective,and stereospecific processes.These advancements provide deeper insight into the reaction progress,challenges,and limitations.We anticipate a better understanding of the underlying mechanistic intricacies will further broaden their applicability in target-directed synthesis.
