The Methodology Research Of Carbene Intermediates Generated From Alkynes

Carbene transfer reaction is one of the most useful tools in the synthetic chemistry.Carbene species were typically generated from the decomposition of diazo-compounds.Recently,many efforts have been made to investigate the carbene species in situ generated from the low-toxicity and safer alkyne compounds.We devoted to the transformation of alkyne to form the carbene intermediate.During the investigation,an efficient catalytic system and the novel synthesis methods were developed,which provide potential synthetic methods for the ring compounds synthesis.This dissertation was divided into three parts as follow:1.NHC-AuCl/Selectfluor: a highly efficient catalytic system for carbene-transfer reactions.The combination of IPrAuCl/Selectfluor was found as a highly efficient catalytic system for the intermolecular carbene transfer reactions with enynones as the carbene precursors.In this work,1 ppm IPrAuCl was efficiently catalyze the reactions,yielding the cyclopropane products and the X-H insertion products(X = Si,O,N)in good yields.The Si-H insertion reaction was especially efficient,the TON and TOF were up to 990,000 and 82,500 h-1,respectively.Moreover,the cyclopropanation reaction can be done even in gram scale.The control reactions suggested that a homogenous Au(?)species might be the real catalyst,which was generated in situ from the oxidation of IPr AuCl by Selectfluor.2.Proton/metal-catalyzed tandem benzofuran annulation/carbene transfer reaction.Various benzofuryl-substituted cyclopropanes and cycloheptatrienes were obtained with good yields under the dual catalytic condition.The reaction was proposed to proceed through two key intermediates,o-QM and benzofuryl carbene.The DFT-based computational work revealed that the reaction was initiated through the dehydration of o-HBA via a proton shuttle transition state,forming the key intermediate o-QM.The benzofuryl carbene was formed by Rh2(OPiv)4 and then captured by carbon-carbon double bonds.3.Rh(?)-Catalyzed Cycloisomerization of 1,n-Enynal and 1,6-Diynal.The Rh(?)-catalyzed cycloisomerization of 1,n-enynals and 1,n-diynals was investigated.It showed that Rh2(S-BTPCP)4 is highly effective for the cycloisomerization of 1,n-enynals to form formyl-substituted cyclopropane-fused bicyclic compounds in both high yields and enantioselectivities.The furan-fused dihydropyridine was obtained as well from 1,6-diynals with Rh2(S-BTPCP)4.A combined investigation of DFT calculation and experiments was carried out to help understand the reaction mechanism.The reaction was proposed through a tandem 6-endo-dig cyclization/[1,2]-H shift to give the cyclopropane-fused bicyclic compounds;while for 1,6-diynal,a direct [3+2] cyclization followed by [1,2]-H shift was expected to afford the furan-fused dihydropyridine products.Further studies revealed that a formal [3+2] cycloaddition product could be obtained by introducing a donor group at the alkene terminal.Furthermore,the DFT calculation also indicated a double hydrogen-bonding interaction between the formyl C-H and the oxygen atoms of the catalyst,such hydrogen-bonding interaction was proven very important for both efficient transformations of the substrates and asymmetric induction of the reaction.The resulting chiral formyl-substituted cyclopropane-fused bicyclic compound found a series of synthetic utility as chiral building block for various stereoselective syntheses.