Table 1 Optimization of Reaction Conditionsa.

From: A practical preparation of bicyclic boronates via metal-free heteroatom-directed alkenyl sp2-C‒H borylation

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Entry

BX3 (2, n equiv)

A (y equiv)

T (°C)

t (h)

Conversion (%)

Yield(%)b

1

BBr3 (2a, 2.0)

none

–60

0.5

100

35

2

BF3 (2b, 2.0)

none

–60

0.5

0

/

3

BCl3 (2c, 2.0)

none

–60

0.5

100

trace

4

BBr3 (2a, 2.0)

A1 (2.0)

–60

1

<5%

trace

5

BBr3 (2a, 2.0)

A2 (2.0)

–60

1

<5%

trace

6

BBr3 (2a, 2.0)

A3 (2.0)

–60

1

100

38

7

BBr3 (2a, 2.0)

A4 (2.0)

–60

1

100

86

8

BBr3 (2a, 2.0)

A5 (2.0)

–60

1

100

99

9

BBr3 (2a, 2.0)

A6 (2.0)

–60

1

70

60

10

BBr3 (2a, 2.0)

A7 (2.0)

–60

1

100

98

11

BBr3 (2a, 1.5)

A5 (2.0)

–60

2

100

50c

12

BBr3 (2a, 1.5)

A5 (1.5)

–60

2

100

99

13

BBr3 (2a, 1.5)

A5 (1.1)

–60

2

100

99

14

BBr3 (2a, 1.1)

A5 (1.1)

–60

2

100

99

15

BBr3 (2a, 1.1)

A5 (1.1)

–40

2

100

86

16

BBr3 (2a, 1.1)

A5 (1.1)

–80

2

60

60

  1. aReactions were carried out with 1aa (0.2 mmol, 1.0 equiv), BX3 (2, n equiv), base (A, y equiv) in CH2C12 (1.0 mL) under N2 atmosphere, unless otherwise noted.
  2. bDetermined by 1H NMR analysis with mesitylene as an internal standard.
  3. co-Isopropenyl phenol (1bb) was also obtained in 40% yield.
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