Table 1 Screening of conditions for the preparation of 1,1-diborylalkanes from alkenes

From: Nickel-catalyzed synthesis of 1,1-diborylalkanes from terminal alkenes

Entrya

Ni cat.

Ligand

Base

Solvent

Yield (%)b

1

Ni(COD)2

PCy3

LiOMe

PhMe

39

2

Ni(COD)2

PCy3

LiOBut

PhMe

<5

3

Ni(COD)2

PCy3

Cs2CO3

PhMe

22

4

Ni(COD)2

PCy3

NaOBut

PhMe

Trace

5

Ni(COD)2

PCy3

KOBut

PhMe

<5

6

Ni(COD)2

PCpent3

LiOMe

PhMe

Trace

7

Ni(COD)2

PCyPh2

LiOMe

PhMe

Trace

8

Ni(COD)2

IMes.HCl

LiOMe

PhMe

trace

9

Ni(COD)2

Cy-XantPhos

LiOMe

PhMe

62

10

Ni(COD)2

Cy-XantPhos

LiOMe

THF

52

11c

Ni(COD)2

Cy-XantPhos

LiOMe/NEt3

PhMe/THF

78

12

–

Cy-XantPhos

LiOMe/NEt3

PhMe/THF

0

13

Ni(PPh3)4

PCy3

LiOMe

PhMe

0

14

NiCl2(PCy3)2

PCy3

LiOMe

PhMe

12

  1. Standard reaction conditions: 5% Ni(COD)2, 5% Cy-XantPhos, 2.0 equiv. B2pin2, 1.0 equiv. LiOMe, 0.5 equiv. NEt3, 0.55 mL PhMe/THF(v:v/10:1) with Ar protection at 130 °C for 1 h
  2. aFor entry 1–10 and 13–14, 10% Ni(COD)2 and 20% Ligand, at 130 °C for 12 h
  3. bGC yield average of two runs using n-tetracosane as internal standard
  4. cStandard reaction conditions
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