Nickel-Catalyzed Cross-Coupling of Umpolung Carbonyls and Alkyl Halides

Structural Properties
Alkyl halides are halogen-substituted alkanes wherein one or more hydrogen atoms of an alkane is replaced by a halogen atom such as fluorine, chlorine, bromine, or iodine. The carbon atom in an alkyl halide is bonded to the halogen atom, which is sp3-hybridized and exhibits a tetrahedral shape.
Unlike alkyl halides, compounds in which a halogen atom is bonded to an sp2 -hybridized carbon atom of a carbon-carbon double bond (C=C) are called vinyl halides. Whereas aryl...

Chlorine isotopes exist as 35Cl and 37Cl in a 3:1 ratio, while bromine isotopes exist as 79Br and 81Br in a 1:1 ratio. The mass spectrum of alkyl halides typically produces two distinct molecular ion peaks, the molecular ion peak, [M], and the molecular ion plus two, [M + 2] peak. The relative heights of these two peaks are proportional to the isotopic abundance ratios of the halide. For example, 2‐chloropropane and 1‐bromopropane display two peaks with relative peak heights in a 3:1 and...

This lesson delves into the conversion of alcohols to corresponding alkyl halides and the mechanism of action for different reagents. Typically, the hydroxyl group is first protonated to convert it to a stable leaving group. Consequently, based on the starting alcohol, the mechanism undergoes either of the nucleophilic substitution routes, SN1 or SN2. Tertiary alkyl halides are made using the two-step SN1 mechanism that occurs via a carbocation intermediate, which is stabilized by...

Ethers are generally unreactive and unsuitable for direct nucleophilic substitution reactions since the alkoxy groups are strong bases and, therefore, poor leaving groups. However, ethers readily undergo acidic-cleavage reactions. Ethers can be converted to alkyl halides when heated with strong acids such as HBr and HI in a sequence of two substitution reactions.

Radical substitution reactions can be used to remove functional groups from molecules. The hydrogenolysis of alkyl halides is one such reaction, where the weak Sn–H bond in tributyltin hydride reacts with alkyl halides to form alkanes. Here, the reagent Bu3SnH yields tributyltin halide as a byproduct.
The bonds formed in this reaction are stronger than the bonds broken, making it energetically favorable. The reaction follows a radical chain mechanism similar to radical halogenation reactions,...

Unlike mitosis, meiosis aims for genetic diversity in its creation of haploid gametes. Dividing germ cells first begin this process in prophase I, where each chromosome—replicated in S phase—is now composed of two sister chromatids (identical copies) joined centrally.
The homologous pairs of sister chromosomes—one from the maternal and one from the paternal genome—then begin to align alongside each other lengthwise, matching corresponding DNA positions in a process...