Deconstructive fluorination of cyclic amines by carbon-carbon cleavage

Abstract

Deconstructive functionalizations involving scission of carbon-carbon double bonds are well established. In contrast, unstrained C(sp3)–C(sp3) bond cleavage and functionalization have less precedent. Here we report the use of deconstructive fluorination to access mono- and difluorinated amine derivatives by C(sp3)–C(sp3) bond cleavage in saturated nitrogen heterocycles such as piperidines and pyrrolidines. Silver-mediated ring-opening fluorination using Selectfluor highlights a strategy for cyclic amine functionalization and late-stage skeletal diversification, establishing cyclic amines as synthons for amino alkyl radicals and providing synthetic routes to valuable building blocks.

Selective valorization of lignin to phenol by direct transformation of C sp2 –C sp3 and C–O bonds

“…HY 30 and HY 40 zeolites have higher concentration of strong acid sites exposed in the mesoporous channels (table S2), affording them higher yields of 1b (entries 1 and 3 of Table 1). However, the acid sites of HY 40 zeolite are less than that of HY 30 (table S2), and thus, the catalytic performance of HY 30 was better than the HY 40 zeolite. Other types of zeolites such as ZSM-5, mordenite, beta, and MCM-41 could not promote the reaction effectively under such conditions (entries 4 to 7).…”

“…The scale-up reaction was performed in 1-liter autoclave (Weihai Xinyuan Chemical Machinery Co. Ltd.). In the reaction, 50.0 g of lignin, 50.0 g of HY 30 , and 600 ml of H 2 O were added into the autoclave. The autoclave was sealed and purged with Ar to remove the air at room temperature and subsequently charged with 0.5 MPa of Ar.…”

“…Thus, the cleavage of the C sp2 -C sp3 bond at mild condition is necessary. Historically, the mild deconstruction of C-C bond has often been realized by coupling this process with simultaneous formation of other bonds, such as C-X (X = C, Si, N, O, S, F …) bond formation (25)(26)(27)(28)(29)(30). The deconstructive functionalization method has limitation in lignin valorization because it involves multiple steps and has low atom economy (7).…”

Radical‐Promoted C−C Bond Cleavage: A Deconstructive Approach for Selective Functionalization

“…In 2018, the group of Sarpong [64] developed the first homolytic CÀCbond cleavage method for the deconstruction/ fluorination of unstrained cyclic amines.T he significance of this chemistry is that the functional group (alcohol in this case), which is indispensable for the cleavage,i si nstalled in situ during the reaction. This aspect is in contrast to all the other methods discussed so far for CÀCb ond cleavage.T his method involves two key steps,each mediated by asilver salt.…”

Ring-opening functionalizations of unstrained cyclic amines enabled by difluorocarbene transfer

“…Despite recent advances in the realm of C-C bond transformations [17][18][19][20] , the selective cleavage of C-N bonds would be a compelling strategy for ring-opening functionalization of cyclic amines. Nonetheless, the process that cleaves and turns C-N bonds into versatile functionalities is still relatively scarce.…”