Methyl (E)-2-methylbut-2-enoate

This compound is typically encountered as a clear, colorless liquid with a strong, sweet, fruity odor reminiscent of ripe strawberries and pineapple. Its molecular formula is C6H10O2, corresponding to a molecular weight of 114.14. The boiling point is approximately 136–138 °C at atmospheric pressure, with a calculated density near 0.92 g/cm³. It is freely soluble in organic solvents including ethanol, acetone, and diethyl ether, but only sparingly soluble in water. The molecule features an α,β-unsaturated ester moiety with a defined (E)-configuration, making it susceptible to polymerization upon prolonged exposure to light and air. It should be stored in tightly sealed containers away from heat, light, and oxidizing agents, preferably under inert atmosphere. The compound is flammable and may cause irritation upon contact, requiring standard laboratory precautions.

Methyl (E)-2-methylbut-2-enoate, commonly known as methyl tiglate, is an unsaturated ester derived from tiglic acid. Its structure comprises a fourcarbon chain with a double bond between the second and third carbons, a methyl substituent at the second carbon, and a methyl ester group at the terminus. The (E)-configuration defines the relative orientation of the methyl and ester groups across the double bond, imparting specific conformational preferences. This compound belongs to the family of tiglates, which are naturally occurring esters found in various essential oils and fermentation products. The conjugated ester system renders it reactive toward Michael additions and DielsAlder cycloadditions, making it a valuable building block in organic synthesis. Its pleasant fruity aroma also makes it a soughtafter ingredient in flavor and fragrance compositions.

Flavor and Fragrance Ingredient
Methyl tiglate is widely employed in the flavor industry to impart sweet, fruity, and berrylike notes to food products, including confectionery, beverages, and baked goods. In perfumery, it contributes to fresh, fruity top notes in floral and fruity compositions, enhancing the complexity of fragrances used in soaps, lotions, and cosmetics. Its volatility and stability under typical formulation conditions make it a reliable component for creating longlasting scent profiles.

Building Block in Organic Synthesis
The α,β-unsaturated ester system serves as a versatile Michael acceptor, enabling conjugate additions with various nucleophiles such as amines, thiols, and carbanions. It also participates in cycloaddition reactions, including DielsAlder and 1,3-dipolar cycloadditions, providing access to complex cyclic structures. These transformations are exploited in the synthesis of natural products, pharmaceuticals, and agrochemicals where the tiglate moiety appears as a key structural element.

Intermediate in Polymer Chemistry
This unsaturated ester can be copolymerized with other monomers to produce functional polymers with tailored properties. Its double bond participates in radical polymerization, yielding polyacrylates with pendant tiglate groups that can be further modified. Such polymers find applications in coatings, adhesives, and as components in biomedical materials where controlled release or surface functionality is desired.

Biosynthetic and Metabolic Studies
Methyl tiglate and its derivatives are used in biochemical research to study ester metabolism and the biosynthesis of tiglate-containing natural products. It serves as a model substrate for esterases and lipases, enabling investigations of enzyme specificity and catalytic mechanisms. Its presence in plant essential oils also makes it a target for studies on plant secondary metabolism and chemotaxonomy.