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(14) Although the isolated yield of product 11f was low (27% in o-
DCB, see SI), when the reaction was performed in the presence of furan
(6 equiv), an excellent external trapping agent for arynes, the furan
adduct (cf. 15a) was isolated in 52% along with 11f (13%) (see SI). The
overall yield of pyridyne-derived adducts encouraged us to pursue this
type of substrate further.
1. cyano as the diynophile
(15) Rates of HDDA cyclization of, for example, ia24 and ib3 for
comparison with that of 12 (Figure 3).
N
N
N
trap
Δ
R3
TMS
R2
R3
TMS
R2
O
O
HO
a 3,4-pyridyne
pyridines
trap
1,2-DCE or PhH
85 °C, 16–18 h
(t1/2 = ~4 h)
HO
2. cyano in an aza-1,3-diyne
R1
R1
R1
R1
ia
ib
iia (78%)
iib (85%)
Δ
N
N
R1
R2
R3
N
a
b
OMe
Me
OMe
H (CH2)3OAc H
a 2,3-pyridyne
(16) Niu, D.; Willoughby, P. H.; Baire, B.; Woods, B. P.; Hoye, T. R.
Alkane desaturation by concerted double hydrogen atom transfer to
benzyne. Nature 2013, 501, 531–534.
(17) Throughout the manuscript only the major product is shown
along with the ratio of major to minor adducts in instances where
constitutional isomers are formed. The characterization data for both are
provided in the Supporting Information (SI).The structure assignment
was made on the basis of both NOE experiments as well as the significant
chemical shift differences between H3 and H4 in the 1H NMR spectrum
each of pyridine product.
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