Selective Three-Component Coupling for CO₂ Chemical Fixation to Boron Guanidinato Compounds

Abstract

A selective three-component coupling was employed to fix carbon dioxide to boron guanidinato compounds. The one-pot reaction of carbon dioxide, carbodiimides, and borylamines (ArNH)BCH afforded the corresponding 1,2-adducts {R(H)N}C{N(Ar)}(NR)(CO)BCH. Alternatively, the reaction with p-MeOCHNC or 2,6-MeCHNC gave the corresponding isocyanide 1,1-adducts { i-PrHN}C{N(p-Me-CH)}(N i-Pr){CNAr}BCH. The molecular structures of products (2,6- i-PrCHNH)BCH 7, { i-Pr(H)N}C{N(p-MeCH)}(N i-Pr)(CO)BCH 9, {Cy(H)N}C{N( p-MeCH)}(Cy)(CO)BCH 13, and { i-PrHN}C{N( p-MeCH)}(N i-Pr){CNR″}BCH (R″ = p-MeOCH, 2,6-MeCH) 14 and 15 were established by X-ray diffraction. Density functional theory calculations at the M05-2X level of theory revealed that CO fixation and formation of the corresponding adduct is exothermic and proceeds via a nonchelate boron guanidinato intermediate.

Mono- and Dinuclear Asymmetric Aluminum Guanidinates for the Catalytic CO2 Fixation into Cyclic Carbonates

“…All other chemical reagents and solvents were obtained from the usual commercial suppliers and used as received. 1 H and 13 C NMR spectra were recorded on a Bruker Avance-400 spectrometer. Chemical shifts and coupling constants are reported in parts per million and hertz, respectively.…”

“…1 H NMR (400 MHz, CDCl 3 , ppm; see Supporting Information for atom assignment): δ 6.84 (s, 2H, H 9 ), 3.88 (d, J = 9.2 Hz, 1H, N-H, H 5 ), 3.45 (m, 1H, H 2 ), 3.29 (m, 1H, H 4 ), 2.27 (s, 1H, H 11 ), 2.20 (s, 2H, H 12 ), 1.19 (d, J = 6.3 Hz, 6H, H 1 ), 0.99 (d, J = 6.4 Hz, 6H, H 3 ), −0.71 (s, 12H, H 13 ). 13 Synthesis of Complex 2. A dichloromethane solution of 2 equiv of trimethylaluminum (44.05 mg, 0.611 mmol) was added to a dichloromethane solution of diisopropyl ferrocenyl guanidine (200 mg, 0.611 mmol).…”

“…Although there are stoichiometric synthetic routes, the catalytic hydroamination of carbodiimides is a 100% atom-economic procedure that allows the easy preparation of trisubstituted guanidines. , This offers the steric and electronic properties of the ligands to be modulated by means of an appropriate choice of starting reagents in the production of guanidine derivatives. Since 2010, our group has been investigating the preparation of substituted guanidines using cheap ZnEt 2 as catalyst (Scheme ), as well as their use as ligands in guanidinato compounds with early and late transition metals, as well as with elements from the s and p blocks. − This allows the formation of complexes with chelate ligands asymmetrically coordinated to the metal center, regardless of the metals used. Additionally, the presence of two N–H moieties in the guanidine compounds would allow further reactivity for these ligands.…”

“…1 H NMR (C 6 D 6 , 400 MHz, ppm): δ 4.14 (s, 5H, H 9 ), 4.08 (s, 2H, H 7 ), 3.73 (s, 2H, H 8 ), 3.62 (m, 2H, H 2,4 ), 0.96 (m, 12H, H 1,3 ), −0.23 (s, 12H, H 10 ) 13. C{ 1 H} NMR (C 6 D 6 , 101 MHz, ppm): δ 163.95 (C 5 ), 99.27 (C 6 ), 69.51 (C 9 ), 65.31 (C 7,8 ), 53.87, 44.73 (C 4 ), 23.81, 22.05 (C 2 ), −7.58 (C 10).…”

Reactivity of N-Phosphinoguanidines of the Formula (HNR)(Ph2PNR)C(NAr) toward Main Group Metal Alkyls: Facile Ligand Rearrangement from N-Phosphinoguanidinates to Phosphinimine-Amidinates

“…While the mechanism as a whole is unprecedented, some of the steps are supported by previous experimental evidence. For example, although carbodiimide insertion into E−NR 2 bonds is thermodynamically favored in most cases, our group reported the opposite process (i.e., the carbodiimide deinsertion reaction) to take place for certain guanidinato−BR 2 derivatives (BR 2 = BCy 2 27 or BC 8 H 14 28 ) through a mechanism involving a retro [2 + 2] cycloaddition, thus rendering an equilibrium at room temperature between the deinsertion products (carbodiimides and amino-boranes) and the parent guanidinato compounds. A similar equilibrium was found for the reaction of LiNMe 2 and the bulky carbodiimide C(N t Bu) 2 , 29…”