Transition-metal-free PhI(OAc)₂-promoted highly selective hydroboration of terminal alkynes under air

Abstract

A new transition-metal-free PhI(OAc)2-promoted highly selective hydroboration of terminal alkynes with bis(pinacolato)diboron has been developed at room temperature under air.

Tuning Polarity of Cu-O Bond in Heterogeneous Cu Catalyst to Promote Additive-free Hydroboration of Alkynes

“…These results manifest that active sites of both the SAS Cu catalysts are exposed to the surface of ceria, and the discrepant activities probably derive from the distinct electronic structures of their SAS Cu active centers. According to the generally acceptable mechanism of Cu-catalyzed hydroboratioin of alkynes, 56,57 the role of additive NaOEt can be assigned to activate the Cu precatalyst or B 2 Pin 2 for inducing active copper-boryl species. However, this hydroboration reaction cannot occur when trifluoromethanesulfonic acid (HOTf) and sulfuric acid (H 2 SO 4 ), which can only activate B 2 Pin 2 are used as the additive instead of NaOEt (Scheme S4).…”

Overview of Regioselective and Stereoselective Catalytic Hydroboration of Alkynes

“…Another metal‐free catalytic hydroboration system, which deals with the use of PhI(OAc) 2 as a catalyst, has been reported. Notably, various terminal alkynes were hydroborated in good yields with excellent regio‐ and stereoselectivity (Scheme 26a) [99] . A plausible mechanism for PhI(OAc) 2 ‐catalyzed hydroboration is given in Scheme 26b.…”

“…Notably, various terminal alkynes were hydroborated in good yields with excellent regioand stereoselectivity (Scheme 26a). [99] A plausible mechanism for PhI(OAc) 2 -catalyzed hydroboration is given in Scheme 26b. At first, the intermediate 90 is generated with the reaction between B 2 pin 2 and NaO t Bu, which when reacted with the iodonium reagent (89) produces the key intermediate (91) containing the IÀ B bond.…”

Progress in organocatalysis with hypervalent iodine catalysts

“…215 Synthetically important E-vinyl boronates 420 were prepared by Wei and co-workers by the hydroboration of terminal alkynes 418 with bis(pinacolato)diboron (B 2 pin 2 ) 419 using catalytic amounts of PhI(OAc) 2 1 in the presence of t BuONa and EtOH as the hydrogen donor in air (Scheme 120). 217 Aromatic as well as aliphatic terminal alkynes 418 gave moderate to good yields with good regio-and stereoselectivity. A facile and effective iodine(III)-catalysed synthesis of pharmacologically important trideuteroalkoxylated quinoxalinones 424 was established by Shen and co-workers using a crossdehydrogenative coupling of quinoxalinones 422 with deuterated alcohols 423 and 4-iodotoluene 149 as precatalyst in the presence of peracetic acid (Scheme 121).…”