A preparation of haloalkylidene cyclopentanones

Cyclizations of Alkynes: Revisiting Baldwin’s Rules for Ring Closure

“…The resulting vinyl radical was trapped via hydrogen abstraction from products. 133 In a similar way, conjugation with a β-pyridine moiety does not affect the exocyclic regioselectivity either (Scheme 34). 134 Because of the stereoelectronic features of the alkyne moiety, the incipient radical in these two examples remains orthogonal to the internal π-systems in the transition state and, thus, the 6-endo-dig closure does not receive any conjugative assistance.…”

“…While polarization controls the regioselectivity of anionic cyclizations effectively (Scheme and Scheme ), Weavers et al observed 5-exo-dig closure for silyl, aryl alkyl substituted alkynes instead of radical conjugate addition (RCA) which would provide the 6-endo products . In a similar way, conjugation with a β-pyridine moiety does not affect the exocyclic regioselectivity either (Scheme ) .…”

Photochemical benzylic bromination in continuous flow using BrCCl3 and its application to telescoped p-methoxybenzyl protection

“…26 As a reagent, BrCCl 3 is readily available, 27 does not have any significant identified health concerns 28 and is not listed as an ozone depleting substance. 29 It has seen numerous applications in atom-transfer radical addition (ATRA) reactions, both photochemically 30,31 or by classical radical methods [32][33][34][35] and also as an oxidizing agent; used directly, [36][37][38] or within a photoredox catalytic cycle. [39][40][41][42] It was anticipated that by utilizing advancements in light source and reactor technology, an improved methodology could be developed.…”