Related Experiment Video
Updated: Jun 9, 2026

Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy
Published on: November 9, 2019
Reactions of boron amidinates with CO2 and CO and other small molecules
Meghan A Dureen1, Douglas W Stephan
1Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.
Abstract:
Reaction of Piers' borane, HB(C(6)F(5))(2), with either tert-butyl or isopropyl carbodiimide cleanly affords the boron amidinates HC(RN)(2)B(C(6)F(5))(2) [R = iPr (1), tBu (2)]. These species undergo a variety of insertion reactions. For example, treatment of 1 with CO(2) or excess carbodiimide gives HC(iPrN)(2)(CO(2))B(C(6)F(5))(2) (3) or HC(iPrN)(2)C(iPrN)(2)B(C(6)F(5))(2) (4), respectively. Similarly, exposure of 1 or 2 to 1 atm CO gives HC(RN)(2)(CO)B(C(6)F(5))(2) [R = iPr (5), tBu (6)], while reaction of 1 with CNtBu gives HC(RN)(2)(CNtBu)B(C(6)F(5))(2) [R = iPr (7), tBu (8)]. Compounds 1 and 2 also react with benzaldehyde, resulting in the formation of HC(RN)(2)(PhHCO)B(C(6)F(5))(2) [R = iPr (9), tBu (10)]. Compound 1 also reacts with MeCN to give HC(iPrN)(2)(MeCN)B(C(6)F(5))(2) (11) and effects heterolytic C-H cleavage to afford HC(iPrN)(iPrNH)(PhCC)B(C(6)F(5))(2) (12). In contrast, the species PhC(iPrN)(2)B(C(6)F(5))(2) (14) derived from PhC(iPrN)(2)BCl(2) (13) failed to react with any of the above substrates. These data, in addition to the isolation of HC(iPrN)(2)(C(6)F(4))BF(C(6)F(5)) (15), the product of thermolysis of 1, provide further support for the notion that the transient "open-chain" form of these amidinates is present in solution.
Related Concept Videos
Hydroboration-Oxidation of Alkenes
Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
Preparation of Amines: Reductive Amination of Aldehydes and Ketones
Regioselectivity and Stereochemistry of Hydroboration
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Preparation of Alcohols via Addition Reactions
The acid-catalyzed addition of water to the double bond of alkenes is a large-scale industrial method used to synthesize low-molecular-weight alcohols. An acidic atmosphere is required to allow the hydrogen in the water molecule to act as an electrophile and attack the double bond in an alkene. The addition of a proton to the double bond creates a carbocation intermediate. The proton preferentially bonds to the less substituted end of the double bond to create a more stable carbocation...
Alcohols from Carbonyl Compounds: Reduction
Catalytic hydrogenation is similar to the reduction of an alkene or alkyne by adding H2 across the pi bond in the presence of transition metal catalysts like Raney Ni, Pd–C, Pt, or Ru. Aldehydes and ketones can be reduced by this method, often under mild to moderate heat (25–100°C) and...

