This book introduces readers to the use of formic acid for efficient organic synthesis. It describes the N-methylation of aromatic and aliphatic amines with formic acid using a boron-based catalyst [B(C6F5)3] in combination with silanes and without the need for an expensive transition metal catalyst. It also shows that formic acid interacts with alkynes and allyl alcohols through a carbonylation process that generates carbon monoxide in situ from nickel and palladium catalysis, respectively, doing away with the need to use high-pressure CO gas and offering a user-friendly and practical method for preparing functionalized , - and , -unsaturated carboxylic acids. The findings presented not only enrich the field of ‘C1 chemistry,’ but also support the advancement of green and sustainable chemistry.