Benzofurans are among the most popular structural units in bioactive natural products,h owever,t he synthesis of such structures by radical cyclization cascade reactions is rare. Herein, we report am ild and broadly applicable method for the construction of complex benzofurylethylamine derivatives through au nique radical cyclization cascade mechanism. Single-electron transfer (SET) from 2-azaallyl anions to 2-iodo aryl allenyl ethers initiates aradical cyclization that is followed by intermolecular radical-radical coupling. This expedient approach enables the synthesis of ar ange of polycyclic benzofurans that would otherwise be difficult to prepare.
Here we report a unique transition-metal-free
C(sp3)–H/C(sp3)–H coupling of
cycloalkanes at room temperature. Unactivated
cycloalkanes and 2-azaallyls underwent the combination process of
single-electron transfer (SET) and hydrogen atom transfer (HAT) to
deliver a wide variety of cycloalkane-functionalized products. This
expedient approach enables C(sp3)–H/C(sp3)–H coupling of cycloalkanes under mild conditions without
transition metals, initiators, and oxidants.
Allylation of nucleophiles with highly reactive electrophiles like allyl halides can be conducted without metal catalysts. Less reactive electrophiles, such as allyl esters and carbonates, usually require a transition metal catalyst to facilitate the allylation. Herein, we report a unique transition-metal-free allylation strategy with allyl ether electrophiles. Reaction of a host of allyl ethers with 2-azaallyl anions delivers valuable homoallylic amine derivatives (up to 92%), which are significant in the pharmaceutical industry. Interestingly, no deprotonative isomerization or cyclization of the products were observed. The potential synthetic utility and ease of operation is demonstrated by a gram scale telescoped preparation of a homoallylic amine. In addition, mechanistic studies provide insight into these C(sp3)–C(sp3) bond-forming reactions.
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