A decade update on solvent and catalyst-free neat organic reactions: a step forward towards sustainability

Abstract

The keen success has been achieved towards the synthesis of new product and process as the twelve principle of "Green Chemistry" was formulated in 1990s. These products and processes are more compatible with human health, society and the environment. In this review a collection of researches has been documented from the view point of green chemistry. The main theme of this review is neat reactions which are solvent and catalyst-free reactions. Neat reactions in absence of any solvents and catalysts with the concise forms of microwaves, ball milling neat reactions have been described.

Mechanochemical Knoevenagel condensation investigated in situ

“…The syntheses are either solvent-free or require only a minimum amount of solvent. Consequently, solvation and desolvation phenomena can be neglected [4–6]. Mechanochemical syntheses of organic systems provide for example an efficient method for cocrystal screening [7–9], an increased product selectivity [2,10–12], and a pathway to new products, which are inaccessible via traditional methods [3,13–14].…”

Chemoselective and Catalyst‐Free O‐Borylation of Silanols: A Facile Access to Borasiloxanes

“…The reactions take place under mild conditions (RT, air atmosphere) within the atom‐economy approach (H 2 as the only by‐product). Last but not least, in the case of liquid reagents, the reactions proceeded in solvent‐free conditions (sfrc) …”

Fast highly efficient 'on-solvent' non catalytic cascade transformation of benzaldehydes and 4-hydroxycoumarin into bis(4-hydroxycoumarinyl)arylmethanes

“…[39][40][41][42][43] Thus, further minimization of the quantity of solvent and reaction time have been investigated showing improved yields (entries 5-8, Table 1) while no-solvent conditions result in some yield's decrease (entry 12, Table 1). …”