Taming 3-Oxetanyllithium Using Continuous Flow Technology.

The oxetane ring has evolved as a useful bioisostere for dimethyl and carbonyl groups for the improvement of physiochemical properties of drug candidates. Herein, we report the generation and utilization of highly unstable 3-oxetanyllithium as a hitherto unexplored nucleophile leveraging flash technology. A range of different electrophiles are suitable reaction partners in this protocol, and we demonstrate the utility of this protocol in late-stage pharmaceutical analogue synthesis.

Trends in carbazole synthesis - an update (2013-2023).

The interest of scientists in the carbazole core has risen steadily over the last 30 years, particularly over the last decade given its presence in several active pharmaceutical ingredients, functional materials and a wide range of biologically active natural products. The continuous development of more efficient, more (regio-)selective and "greener" methodologies to access the carbazole core is thus imperative. This review compares and evaluates synthetic strategies towards the carbazole core that have been reported since 2013, with a focus on their applicability towards the total synthesis of carbazole-containing natural products.

An entry to 2-(cyclobut-1-en-1-yl)-1H-indoles through a cyclobutenylation/deprotection cascade.

A transition-metal-free strategy for the synthesis of 2-(cyclobut-1-en-1-yl)-1H-indoles under mild conditions is described herein. A series of substituted 2-(cyclobut-1-en-1-yl)-1H-indoles are accessed by a one-pot cyclobutenylation/deprotection cascade from N-Boc protected indoles. Preliminary experimental and density functional theory calculations suggest that a Boc-group transfer is involved in the underlying mechanism.

Recent advances in the synthesis of α-amino ketones.

Due to the importance of the amino ketone motif in synthetic and medicinal chemistry, the number of protocols developed in recent years has considerably increased. This review serves to collate and critically evaluate novel methodologies published since 2011 towards this high value synthon. The chapters are divided by the requisite functionality in the starting material, and an emphasis is placed on discussing functional group compatibility and resultant product substitution patterns. Throughout, applications to medicinal targets are highlighted and mechanistic details are presented, and we further provide a short outlook for future development and emerging potential within this area.

Oxidative Deconstruction of Azetidinols to α-Amino Ketones.

A silver-mediated synthesis of α-amino ketones via the oxidative deconstruction of azetidinols has been developed using a readily scalable protocol with isolated yields up to 80%. The azetidinols are easily synthesized in one step and can act as protecting groups for these pharmaceutically relevant synthons. Furthermore, mechanistic insights are presented and these data have revealed that the transformation is likely to proceed through the ß-scission of an alkoxy radical, followed by oxidation and C-N cleavage of the resulting α-amido radical.

Transition-Metal-Free Access to Heteroaromatic-Fused 4-Tetralones by the Oxidative Ring Expansion of the Cyclobutanol Moiety.

Advances in the transition-metal-free cyclobutanol ring expansion to 4-tetralones under N-bromosuccinimide mediation are described. We have expanded the scope of this ring expansion methodology and investigated the effect substituents on the aromatic ring, and the cyclobutanol moiety, have on the outcome of the reaction. Limitations with certain substituents on the cyclobutanol moiety are also described. Further experimental evidence to support our mechanistic understanding is disclosed, and we now preclude the suggested involvement of a primary radical for this transformation.

Regioselective Transition-Metal-Free Oxidative Cyclobutanol Ring Expansion to 4-Tetralones.

A facile and transition-metal-free ring expansion of the cyclobutanol moiety to 4-tetralones fused to heteroaromatic systems is described. The oxidative ring expansion proceeds rapidly and regioselectively through mediation by N-bromosuccinimide and acetonitrile in satisfactory to good yields. The preparation of precursors and the ring expansion have proven to be scalable and are straightforward to carry out.