It is shown here for the first time that diethyl azodicarboxylate promotes dehydrogenation of tertiaryamines to afford enamines, which subsequently take place in tandem reactions with sulfonyl azides to give the N-sulfonyl amidine derivatives. A number of different substituted tertiaryamines and sulfonyl azides can successfully be coupled, and several functionalized groups are tolerated in this system. The reaction described here is mild, general, and efficient, thus providing an extremely preferable method for synthesis of a variety of N-sulfonyl amidine derivatives.

With a growing toolbox of surfactantmediated chemistry in water and an increased number of scaled-up transformations has come tremendous learning [for example, see: Lipshutz, B. H.; et al. The Hydrophobic Effect Applied to Organic Synthesis: Recent Synthetic Chemistry "in Water". Chem. -Eur. J. 2018, 24 (26), 6672−6695]. These opportunities now reside within a few expert groups, and while all of the details are far from fully understood or still under development, substantial know-how has been gained in both reaction process and synthesis design. Herein we share some of the fundamental principles inherent to micellar catalysis and illustrate them on a particularly challenging case involving a Suzuki−Miyaura cross-coupling. The complete structures of the active pharmaceutical ingredient (API) and the intermediates are not fully disclosed for confidentiality reasons but can nevertheless serve as illustrative of the importance of factors that, unlike traditional chemistry in organic solvents, can be crucial to a successful outcome (e.g., lipophilicity). The API used as an example for this discussion bears significant commonality with a large number of other targets associated with the formation of a biphenyl array as well as the presence of an amide and products resulting from nucleophilic aromatic substitutions (S N Ar). Hence, we look to utilize these prior learnings and can now rapidly apply them to the design of optimal conditions for several other important transformations.

A zirconium/nickel-mediated one-pot synthesis of ketones is reported. In the presence of Zn or Mn, Cp ZrCl was found to dramatically accelerate the coupling and suppress side product formation via an I→SPy displacement at the same time. Unlike Zn/Pd- and Fe/Cu-mediated one-pot ketone syntheses, the new method is effective for nucleophiles bearing OR or equivalent functional groups at the α-position. A mechanism comprising a nickel catalytic cycle, a zirconium catalytic cycle, and Zr→Ni transmetalation is proposed, and Cp ZrCl and/or low-valent Zr species are suggested to play crucial dual roles.

Unified, efficient, and scalable syntheses of the halichondrin natural products are reported. A newly developed Zr/Ni-mediated one-pot ketone synthesis was used to couple the two halves of the final product at a late stage in the synthesis. With the use of a slight excess of the left halves, the desired ketones were isolated in yields of 80-90 %. The halichondrins were obtained from these ketones in two steps, namely desilylation and [5,5]-spiroketal formation. The new synthetic route was effective for the total synthesis of all members in the homohalichondrin subgroup. The scalability of this process was demonstrated with halichondrin B; 150 mg of halichondrin B (68 % overall yield) were obtained from 200 mg of the right-half precursor.

The technology of surfactant chemistry is employed for amide bond construction via the reaction of acyl chlorides with amines in 2 wt % TPGS-750-M aqueous solution. Specifically, this highly efficient method enables a chromatography-free scalable process and recycling of the TPGS-750-M solution.

A stereocontrolled synthesis of the left halves of halichondrins was reported. An intramolecular oxy-Michael reaction under basic conditions was used to construct the [6,6]-spiroketal in a stereocontrolled manner. With this approach, the left halves of halichondrins, homohalichondrins, and norhalichondrins were synthesized.

The right halves of halichondrins A-C were synthesized by coupling the common C20-C37 building block 9 with the C1-C19 building blocks 10a-c, respectively. Catalytic, asymmetric Ni/Cr-mediated coupling was used for three C-C bond formations. For all cases, the stereochemistry was controlled with the Cr catalyst prepared from the chiral sulfonamide identified via the toolbox approach. For (3 + 4)-, (6 + 7)-, and (9 + 10)-couplings, the stereoselectivity of 28:1, >40:1, and ∼20:1 was achieved by the Cr catalysts prepared from (S)-H, (S)-I, and (R)-L, respectively. Unlike the first and second couplings, the third coupling used the structurally complex nucleophile. It was demonstrated that the coupling efficiency was excellent even with the electrophile/nucleophile molar ratio = 1.0/1.1. In addition, the third coupling was achieved with the substrate bearing a free hydroxyl group. The products obtained in the Ni/Cr-mediated couplings were converted to the right halves of halichondrins A-C in excellent overall yields. The right halves of halichondrins A-C (1a-c) were synthesized in 28, 24, and 24 steps from commercial d-galactal in 13.4%, 21.1%, and 16.7% overall yield, respectively.

A robust and sustainable C(sp2)-C(sp3) cross- electrophile coupling was developed via nickle/copper synergistic catalysis under micellar conditions. This protocol provided a general method to access alkylated arenes with good to...