Cyclizations via Frustrated Lewis Pairs: Lewis Acid Induced Intramolecular Additions of Amines to Olefins and Alkynes

Reaction of Frustrated Lewis Pairs with Conjugated Ynones‐Selective Hydrogenation of the Carbon–Carbon Triple Bond

“…[1] They add to alkenes and alkynes, [2] add to various carbonyl compounds, including carbon dioxide, [3] and undergo unique 1,4-addition reactions to conjugated enynes and diynes to yield zwitterionic cumulene derivatives. [4] Most notably many FLPs split dihydrogen heterolytically, some reversibly, and are able to transfer the resulting P/B or N/B bonded H + /H À pair to selected unsaturated substrates.…”

“…These compounds were characterized by C,H elemental analysis, spectroscopy, and X-ray crystal structure analysis (see Figure 1 for a representative example; for further details see the Supporting Information). Compound 7 c (R 1 = tBu) as a typical example exhibits a non-planar eight-membered core structure (B1-O3 1.501(3) , P1-C6 1.835 (2) ) that contains a close to linear allene substructure (C4-C5 1.324(3), C5-C6 1.311(3) ; angle C4-C5-C6 172.7 (2) [5b]…”

Capture of NO by a Frustrated Lewis Pair: A New Type of Persistent N‐Oxyl Radical

“…[2] FLPs add to numerous unsaturated substrates such as alkenes and alkynes, carbonyl compounds, azides and even CO 2 or N 2 O. [3,4] For instance, the intramolecular P/B-FLP 1 adds to nitrosobenzene to form the sixmembered heterocycle 2. [5] Nitric oxide (NO) is an important messenger molecule and regulator in biological systems.…”

“…[5] Nitric oxide (NO) is an important messenger molecule and regulator in biological systems. [6] We find that the reactive frustrated Lewis pair 1 cleanly and rapidly reacts with this essential small molecule to form the persistent heterocyclic Noxyl radical "P/B-FLP-NOC" (3). Compound 3 represents a novel type of N-oxyl radical related to the ubiquitous TEMPO radical (4) and its congeners (e.g.…”

BCl3‐Induced Annulative Oxo‐ and Thioboration for the Formation of C3‐Borylated Benzofurans and Benzothiophenes

“…Our studies commenced by combining equimolar BCl 3 and N , N ‐dimethyl‐2‐(phenylethynyl)aniline ( 1 ) for comparison with B(C 6 F 5 ) 3 which formed zwitterion A 7. In contrast to B(C 6 F 5 ) 3 addition of BCl 3 did not lead to a borylated indole with X‐ray diffraction studies revealing it had instead formed 2 (Figure 1), the product from alkyne trans ‐haloboration.…”