Solvent-free Henry and Michael reactions with nitroalkanes promoted by potassium carbonate as a versatile heterogeneous catalyst

The use of a simple weak inorganic base such as potassium carbonate facilitated the formation of carbon-carbon bonds through both the Henry and the Michael reactions with nitrocompounds. The application of this catalyst under environmentally friendly solventless heterogeneous conditions gave satisfactory to good yields of β-nitroalcohols, involving aliphatic and aromatic starting materials, as well as high to excellent yields in the formation of Michael adducts using several different Michael acceptors and nitroalkanes

Exploring new directions in hydrogen transfer chemistry

This thesis describes the development of new routes towards hydrogen transfer chemistry. Transfer hydrogenation is known concept in which hydrogen is transferred from one molecule to another without the use of molecular hydrogen. Borrowing hydrogen is a methodology which employs this concept and is known as hydrogen-autotransfer, as it combines a transfer hydrogenation process with a concurrent reaction on the in situ generated reactive intermediate. This is a great methodology as it doesn’t require toxic and harmful alkylating agents for alkylation. Alcohols are generally used for this methodology which are benign and friendly starting materials producing water as the sole by-product making this process highly atom economic. In this thesis, several methodologies related to hydrogen transfer chemistry have been developed. Initial research was focussed on tandem ruthenium catalysed hydrogen transfer and SNAr chemistry whereby sacrificial additives are used to facilitate the formation of two different sets of compounds following dehydrogenative SNAr chemistry. Several diaryl ethers and secondary amines are formed in good yields. The next project involved the development of a general iron-catalysed methylation using methanol as a C1 building block. The process exhibits a broad reaction scope with a variety of ketones, indoles, oxindoles, amines, and sulfonamides to undergo efficient methylation. This methodology was later applied to the β- methylation of alcohols which is described in a separate chapter in this thesis. The oxindole framework is present in several pharmacologically active compounds. Hence the next part of this thesis involved the development of an efficient iron-catalysed C(3)- alkylation of oxindoles via the borrowing hydrogen approach. This process exhibits a broad reaction scope, allowing primary and secondary aliphatic alcohols to be utilised as alkylating agents with a range of substituted oxindoles. Finally, the last chapter explains a one-pot ironcatalysed conversion of allylic alcohols to α-methyl ketones using methanol as C1 building block

Recent advances in homogeneous borrowing hydrogen catalysis using earth-abundant first row transition metals

The review highlights the recent advances (2013-present) in the use of earth-abundant first row transition metals in homogeneous borrowing hydrogen catalysis. The utility of catalysts based on Mn, Fe, Co, Ni and Cu to promote a diverse array of important C–C and C–N bond forming reactions is described, including discussion on reaction mechanisms, scope and limitations, and future challenges in this burgeoning area of sustainable catalysis

Iron-catalyzed borrowing hydrogen β-C(sp3)-methylation of alcohols

Herein we report the iron-catalyzed β-C(sp3)-methylation of primary alcohols using methanol as a C1 building block. This borrowing hydrogen approach employs a well-defined bench-stable (cyclopentadienone)iron(0) carbonyl complex as precatalyst (5 mol %) and enables a diverse selection of substituted 2-arylethanols to undergo β-C(sp3)-methylation in good isolated yields (24 examples, 65% average yield)

One-pot conversion of allylic alcohols to α-methyl ketones via iron-catalyzed isomerization-methylation

A one-pot iron-catalyzed conversion of allylic alcohols to α-methyl ketones has been developed. This isomerization–methylation strategy utilized a (cyclopentadienone)iron(0) carbonyl complex as precatalyst and methanol as the C1 source. A diverse range of allylic alcohols undergoes isomerization–methylation to form α-methyl ketones in good isolated yields (up to 84% isolated yield)

Iron-catalyzed methylation using the borrowing hydrogen approach

A general iron-catalyzed methylation has been developed using methanol as a C1 building block. This borrowing hydrogen approach employs a Knölker-type (cyclopentadienone)iron carbonyl complex as catalyst (2 mol %) and exhibits a broad reaction scope. A variety of ketones, indoles, oxindoles, amines, and sulfonamides undergo mono- or dimethylation in excellent isolated yields (>60 examples, 79% average yield)

Iron‐catalyzed borrowing hydrogen C‐Alkylation of oxindoles with alcohols

A general and efficient iron-catalyzed C-alkylation of oxindoles has been developed. This borrowing hydrogen approach employs a (cyclopentadienone)iron carbonyl complex (2 mol %) and exhibits a broad reaction scope, allowing benzylic and simple primary and secondary aliphatic alcohols to be employed as alkylating agents. A variety of oxindoles undergo selective monoC(3)-alkylation in good to excellent isolated yields (28 examples, 50- 92% yield, 79% average yield)

Exploring tandem ruthenium-catalyzed hydrogen transfer and SNAr chemistry

A hydrogen-transfer strategy for the catalytic functionalization of benzylic alcohols via electronic arene activation, accessing a diverse range of bespoke diaryl ethers and aryl amines in excellent isolated yields (38 examples, 70% average yield), is reported. Taking advantage of the hydrogen-transfer approach, the oxidation level of the functionalized products can be selected by judicious choice of simple and inexpensive additives

Iron-Catalyzed Methylation Using the Borrowing Hydrogen Approach

A general iron-catalyzed methylation has been developed using methanol as a C1 building block. This borrowing hydrogen approach employs a Knölker-type (cyclopentadienone)iron carbonyl complex as catalyst (2 mol %) and exhibits a broad reaction scope. A variety of ketones, indoles, oxindoles, amines, and sulfonamides undergo mono- or dimethylation in excellent isolated yields (>60 examples, 79% average yield)

Exploring Tandem Ruthenium-Catalyzed Hydrogen Transfer and S_NAr Chemistry

A hydrogen-transfer strategy for the catalytic functionalization of benzylic alcohols via electronic arene activation, accessing a diverse range of bespoke diaryl ethers and aryl amines in excellent isolated yields (38 examples, 70% average yield), is reported. Taking advantage of the hydrogen-transfer approach, the oxidation level of the functionalized products can be selected by judicious choice of simple and inexpensive additives