Room temperature iron catalyzed transfer hydrogenation using n-butanol and poly(methylhydrosiloxane)

Abstract

Reduction of carbon-carbon double bonds is reported using a three-coordinate iron(II) β-diketiminate pre-catalyst. The reaction is believed to proceed via a formal transfer hydrogenation using poly(methylhydrosiloxane), PMHS, as the hydride...

Catalytic Transfer Deuteration and Hydrodeuteration: Emerging Techniques to Selectively Transform Alkenes and Alkynes to Deuterated Alkanes

“…A general alkene transfer hydrodeuteration was demonstrated by Wu and coworkers in 2020 (Scheme 21), [28] but Webster and co‐workers developed an iron catalyst capable of promoting selective alkene transfer hydrodeuteration a year earlier [29] . This work has been expanded in recently published studies [30] …”

“…[29] This work has been expanded in recently published studies. [30] In the reaction developed by Webster and coworkers, the reagents dictate the reaction selectivity; for example, using D 2 NC 6 H 5 and HBpin leads to the anti-Markovnikov addition of H and D (Scheme 23 a), while using H 2 NC 6 H 5 and DBpin leads to the Markovnikov addition of H and D (Scheme 23 b). Under the anti-Markovnikov conditions, selective monodeuteration at the terminal position of the alkene was achieved and deuterated alkanes such as 71 and 72 were regioselectively formed (Scheme 17a).…”

Highly Regioselective Copper‐Catalyzed Transfer Hydrodeuteration of Unactivated Terminal Alkenes

“…The reaction was also evaluated in substrates not containing a pent-1-ene chain (Scheme 4). Allyl benzene, a substrate type known to undergo a thermodynamically driven metal hydride catalyzed alkene isomerization, [30,47] underwent hydrodeuteration with high precision at the terminal alkene (6 a, 61 % yield by 1 H NMR). In a similar fashion, methyl eugenol was precisely deuterated at the terminal position when subjected to the Cucatalyzed transfer hydrodeuteration protocol (6 b, 93 % yield).…”

“…To the best of our knowledge, there exists only two other reports in which metal-catalyzed unactivated terminal alkene transfer hydrodeuteration is performed. [29,30] Although very few examples of unactivated terminal alkene substrates are reported (Scheme 1d), these fundamental works by Webster and co-workers underscore the reactivity and selectivity challenges hindering the development of a general protocol for selectively installing H and D across an unactivated alkene type. Although protocols that employ H 2 , HD or D 2 gas are sometimes reactive with unactivated alkenes, they are insufficient at discriminating between H and D for regioselective hydrodeuteration.…”

“…[31,32] Under catalytic transfer hydrodeuteration conditions, a different challenge arises where catalysts that react with unactivated terminal alkenes can also promote competing alkene isomerization pathways which can lead to mixtures of inseparable isotopomers. [29,30,33] Given the mild and general protocol we established for the transfer hydrodeuteration of alkenyl arene substrates, we were interested in exploring alternate reactions conditions to extend reactivity to unactivated terminal alkenes while retaining the high reaction selectivities found in our initial report. [28] The regioselectivity of the CuÀ H addition across a terminal unactivated alkene is likely influenced by the steric environment of the substrate, where Cu adds to the least sterically hindered alkene position.…”