While preparative
electrolysis of organic molecules has been an
active area of research over the past century, modern synthetic chemists
have generally been reluctant to adopt this technology. In fact, electrochemical
methods possess many benefits over traditional reagent-based transformations,
such as high functional group tolerance, mild conditions, and innate
scalability and sustainability. In this Outlook we highlight illustrative
examples of electrochemical reactions in the context of the synthesis
of complex molecules, showcasing the intrinsic benefits of electrochemical
reactions versus traditional reagent-based approaches. Our hope is
that this field will soon see widespread adoption in the synthetic
community.
New methods and strategies for the direct functionalization of C–H bonds are beginning to reshape the fabric of retrosynthetic analysis, impacting the synthesis of natural products, medicines, and even materials1. The oxidation of allylic systems has played a prominent role in this context as possibly the most widely applied C–H functionalization due to the utility of enones and allylic alcohols as versatile intermediates, along with their prevalence in natural and unnatural materials2. Allylic oxidations have been featured in hundreds of syntheses, including some natural product syntheses regarded as “classics”3. Despite many attempts to improve the efficiency and practicality of this powerful transformation, the vast majority of conditions still employ highly toxic reagents (based around toxic elements such as chromium, selenium, etc.) or expensive catalysts (palladium, rhodium, etc.)2. These requirements are highly problematic in industrial settings; currently, no scalable and sustainable solution to allylic oxidation exists. As such, this oxidation strategy is rarely embraced for large-scale synthetic applications, limiting the adoption of this important retrosynthetic strategy by industrial scientists. In this manuscript, we describe an electrochemical solution to this problem that exhibits broad substrate scope, operational simplicity, and high chemoselectivity. This method employs inexpensive and readily available materials, representing the first example of a scalable allylic C–H oxidation (demonstrated on 100 grams), finally opening the door for the adoption of this C–H oxidation strategy in large-scale industrial settings without significant environmental impact.
N–N-linked
dimeric indole alkaloids represent an unexplored
class of natural products for which chemical synthesis has no practical
solution. To meet this challenge, an electrochemical oxidative dimerization
method was developed, which was applied as the pivotal step of the
first total synthesis of dixiamycin B. This method is also general
for N–N dimerization of substituted carbazoles and β-carbolines,
providing entry into seldom explored chemical space.
A convenient, general, and high yielding Pd-catalyzed cross-coupling of methanesulfonamide with aryl bromides and chlorides is reported. The use of this method eliminates concern over genotoxic impurities that can arise when an aniline is reacted with methanesulfonyl chloride. The application of this method to the synthesis of dofetilide is also reported.
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