Research On Transition Metal-Catalyzed Oxidative Reactions Of Alkenes

Unsaturated hydrocarbon (including alkenes, alkynes, areans) are important stapleproduct of petroleum and petrochemical industries. And it is also significant precursors inorganic synthesis. In scientific point of view, the functionalization of unsaturated hydrocarbonis of great importance due to promoting the advancement of human material civilization andits core position in scientific development. Up to now there are nine Nobel Prizes in chemistryabout the unsaturated hydrocarbons. In2010, the palladium catalyzed Heck-type reaction,recognized with Nobel Prized, has become a powerful tool to prepare substituted olefins.Recently, the oxidative cross-coupling reactions, such as cross-dehydrogenative couplings,the oxidative coupling between two nucleophiles, have attracted increasing interest. Alkenesare of the following characteristic: accessibility, diversity and reactivity. So my research workis focused on transition-metal-catalyzed oxidative coupling reactions between alkenes and theother nucleophiles.The Heck-type reactions and the Wacker-type reactions are the two importanttransformations for alkenes. And β-H elimination is one of the most fundamental reactionclasses in organometallic chemistry, and is the key mechanistic motif of Wacker-type andHeck-type reactions. alkyl C(sp3)-PdIIintermediate generally afford the facile β-H eliminationproducts. So how to suppress the β-H elimination and functionalize the alkyl-PdIIintermediateis of great importance. That was the first part of my doctoral research work. The second partof my doctoral research work was realizing the selective β-H elimination when theelectronically non-biased olefins were used for Heck-type reactions.In this context, we have studied the transition-catalyzed oxidative functionalization ofalkenes and alkynes. The details are summarized as following:(1) The discovery of new transformation through olefins difunctionalization continues to attract broad interestdue to their high potential for application in natural product and bioactive compound synthesis. The Pd and Oscatalyzed difunctionalization of alkenes has been widely applied in laboratorial and industrial synthesis. It issurprising, however, that among these difunctionalization reaction, few can achieve the formation foC(sp3)-C(sp3) bonds, despite their ubiquitous nature. In this paper, the cheap and low toxic copper salt realizedthe carboesterification of alkene with cheap acetic anhydride. The copper-mediated intermolecualr cycloadditionwith subsequent C(sp3)-H/C-O bond cleavage and C(sp3)-C(sp3)/C-O bond formation provide an expedient routeto diverse lactones from simple precursors.(2) As our continuous interest in transition metal catalyzed difunctionalization of olefins,we designed the palladium-catalyzed intermolecular carboesterification of alkenes withalkynes to synthesize–methylene-γ-lactones. Interestingly, highly selective (E)-–methylene-γ-lactones was formed through palladium catalyzed intermolecularcarboesterification of alkenes with alkynoates, while the stereoselectivites can be switched bya simple modification, the carboesterification of alkenes with alkynamides at roomtemperature. In addition,–methylene-γ-lactone skeleton is an important moiety in naturalproducts and exhibits potential biological activities.(3) A new and convenient method to form multifunctional heterocycles was described inPdII-catalyzed difunctionalization of olefins with alkynamides. Remote donor groups in theterminal olefins, cooperating with amide in alkynamides, promoted C(sp3)-O bond formationby suppressing the β-H elimination and regulated the carboesterification andcarboetherification of olefins. We respectively realized the highly selective synthesis ofnaturally occurring α-methylene-γ-lactones and tetrahydrofurans, especially the spirocycliccompounds.(4) A variety of β-aryl ketones and aldehydes were facilely synthesized via aPd(II)/Ag2CO3-mediated decarboxylative Heck type reaction between readily availablebenzoic acid derivatives and allylic alcohols under mild conditions. The control experimentsindicated that this transformation may proceed via a hydrogen migration process.(5) A highly selective β-H elimination in the Pd(II)-catalyzed intermolecular oxidativecoupling reaction was reported, inspired by the fundamental Heck and Wacker processes. The(hetero)aryl-PdX species, originating from C-H activation step or desulfonyl hydrazides,coupled with allylic alcohols using oxygen as the sole oxidant. This reaction provided a newand convenient method for constructing naturally occurring biologically active β-(hetero)arylketone and aldehyde skeletons.(6) As pioneered by Fujiwara and Moritani, the transition metal catalyzed C-H activationand oxidative olefination has made great advances. Though those transformations have beenextensively utilized in organic synthesis, a main restrictive limitation was that the olefins wereusually limited to electronically biased olefins, such as a styrene or an,β-unsaturatedcarbonyl. In this work, we report the Rh(III)-catalyzed (hetero)arenes C-H bond oxidativealkylation with electronically nonbiased allylic alcohols to afford the functional β-aryl ketones.It is also a supplementary approach to the C-H alkylations. Moreover, acetanilides and allylicalcohol was transformed to the1,2-disubstituted indulines under corresponding conditions.This method provides efficient and robust synthesis of functional β-aryl ketones and indolinesin good yield with excellent regioselectivity, even the reaction runs at3g scale. The catalyticsystems have good functional group tolerance, such as CONR2, NHAc, NO2, CF3, CN, Cl, Br and I.