Studies On Green Synthetic Reactions Based On Formic Acid From Biomass

The development of green sustainable methods,that utilize inexpensive and easily available feedstocks for an efficient organic synthesis,is continues to be the major goal of chemical research.Especially,using the "greener" and "renewable"materials substituted of hazardous and waste-generating reagents and precursors is one of the significant tasks for both academic research and industrial production.Formic acid(HCOOH),a renewable bulk chemical derived from the hydrolysis and oxidation of lignocellulose extracted from agricultural and forestry waste and energy crops,is non-toxicity,biodegradability and convenient for storage and transportation.Due to its special structure,formic acid as a C1 building block has a very important application in organic synthesis.Formic acid can be used as formylation reagents,methylation reagents,as well as the substitute for carbon monoxide using in carbonylation reactions.Thus,studies on green synthetic reactions based on formic acid not only enrich and develop the field of "C1 chemistry",but also accord with the direction of the development of green sustainable chemistry.In the first chapter of this thesis,the conversion of formic acid as C1 source in organic synthesis is reviewed.Formic acid can be used as a protecting group for amine during peptide synthesis.Besides,it can be used for the N-methylation conversion of amines,instead of methyl iodide,dimethyl sulfate and other toxic methylation reagents.Carbon monoxide(CO)has been widely used as a carbonylation reagent in industrial processes.However,due to its high toxicity and flammability,the application of carbon monoxide in laboratory organic synthesis and fine chemicals was limited.Therefore,it is very important to seek carbon monoxide substitutes for carbonylation reactions.Recently,considerable efforts have been devoted to the development of formic acid as CO surrogate.The corresponding aldehydes,ketones,or acids can be obtained through the reactions of formic acid with aryl halides,alkenes,alkynes,or aromatic hydrocarbons.N-methyl structural units are ubiquitous in pharmaceutical intermediates and fine chemicals.Precious metal catalysts,such as rhodium,platinum,can be used to catalyze the N-methylation conversion of amines with formic acid as methylation reagent.In chapter 2,we show that a boron-based catalyst[B(C6F5)3]in combination with polymethylhydrogensiloxane can catalyze the straightforward N-methylation of aromatic amines and aliphatic amines,using formic acid in the presence of a silane as reducing agent with highly efficient,good selectivity and good functional group compatibility.In addition,the aromatic imines can also be converted directly through hydrogenation and N-methylation in the catalytic system.Hydrocarboxylation of alkynes is an important strategy to access a,β-unsaturated carboxylic acids.Although the palladium-catalyzed hydrocarboxylation of acetylene with formic acid to produce acrylic acid has been developed,it is still a challenge to achieve the reaction between alkynes and formic acid using cheap metals to form various a,β-unsaturated carboxylic acids.In chapter 3,we have demonstrated that the combination of Ni(Ⅱ)salt with a bisphosphine ligand and catalytic amount of acid anhydride can catalyze atom-economic hydrocarboxylation of a broad range of alkyne with formic acid.The operational simplicity,generality,and remarkable functional group compatibility make this reaction a user-friendly method to prepare functionalized α,β-unsaturated carboxylic acids.Some functional groups which are sensitived in the reducing system or acidic system,such as double bond,aldehyde,cyano,ester,amide,boron ester and carbonyl group,can be well tolerated.Besides,the reaction has a high yield at the gram scale,and has a good prospect of industrial synthesis and application.β,γ-Unsaturated carboxylic acid is an important intermediates in the organic synthesis and chemical industries.Transition metal-catalyzed reaction of allyl alcohol derivatives with carbon monoxide is the important method for preparing β,y-unsaturated carboxylic acids.In chapter 4,we developed a method for the preparation of β,γ-unsaturated carboxylic acids by palladium-catalyzed allyl alcohol with formic acid and without using the high-pressure CO gas.The anhydride has a dual role:to activate an allylic alcohol and to generate a mixed acid anhydride with formic acid to generate CO in situ.The reaction has excellent chemo-,regio-,and stereoselectivity,a wide range of substrates,and good compatibility of functional group,providing a more practical method for the preparation of β,γ-unsaturated carboxylic acids.