Continuous Flow Acylation of (Hetero)aryllithiums with Polyfunctional N,N-Dimethylamides and Tetramethylurea in Toluene

Synthesis of Unsymmetrical Ketones Using Chelation-Controlled Sequential Substitution of N-Triazinylamide/Weinreb Amide by Organometallic Reagents

N-(2,4-Dimethoxy-1,3,5-triazinyl)amide was found to exhibit similar behavior to N-methoxy-N-methylamide (Weinreb amide) but higher reactivity for nucleophilic substitution by organometallic reagents. Triazinylamide suppresses overaddition, leading to the formation of a tertiary alcohol by the chelating ability of the triazinyl and carbonyl groups. Ureas possessing both triazinylamino and methoxy(methyl)amino groups underwent sequential nucleophilic substitution with different organometallic reagents, which furnished unsymmetrical ketones without any detectable tertiary alcohols.

Taming Highly Unstable Radical Anions and 1,4-Organodilithiums by Flow Microreactors: Controlled Reductive Dimerization of Styrenes

The reduction of styrenes with lithium arenide in a flow microreactor leads to the instantaneous generation of highly unstable radical anions that subsequently dimerize to yield the corresponding 1,4-organodilithiums. A flow reactor with fast mixing is essential for this reductive dimerization as the efficiency and selectivity are low under batch conditions. A series of styrenes undergo dimerization, and the resulting 1,4-organodilithiums are trapped with various electrophiles. Trapping with divalent electrophiles affords precursors for useful yet less accessible cyclic structures, for example, siloles from dichlorosilanes. Thus, we highlight the power of single-electron reduction of unsaturated compounds in flow microreactors for organic synthesis.

Potassium tert-Butoxide Facilitated Amination of Carboxylic Acids with N,N-Dimethylformamide

Herein a practical and efficient potassium tert-butoxide (KO t Bu)-facilitated amination of carboxylic acids with N,N-dimethylamine is described. In the presence of catalytic amount of KO t Bu, a variety of aliphatic and aromatic carboxylic acids are transformed to N,N-dimethylamides using DMF as the dimethylamine reagent with the assistance of trimethylacetic anhydride. The applicability of this protocol is demonstrated by late-stage dimethylamidation of complex drug molecules. A plausible reaction mechanism involving KO t Bu-facilitated in situ amine generation from formamide decomposition and anhydride-mediated condensation is proposed on the basis of mechanistic investigations.