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unique. The ratio mainly depended on the combined effect of
the electron pushing and pulling ability of the groups at C2
and C3. Even the weak polarity of the double bond can lead to
significant s-bond selectivity of the reaction. In these
examples, 3g had the worst ratio (2:1), but we have to point
out that it is just caused by the electron pushing effect of
a methyl group. As long as the electron pushing or pulling
effect was properly enhanced, the reaction showed attractive
selectivity (3e, 3 f, 3h–3n). When electron-donating and
electron-withdrawing groups were used cooperatively in cy-
clopropenes, the corresponding product become a unique
isomer (3o–3v). For the efficient synthesis of 3u and 3v from
cyclopropenes with electron-deficient double bond, the ligand
P(p-CF3C6H4)3 needed to be replaced with a relatively more
electron-donating ligand P(2-furyl)3. To further confirm the
structure of the products, we measured the single crystals of
3j, 3u, and 3v, respectively.[16] These results demonstrated
that the selectivity of representative product 3j was consistent
with our inference from the model reaction and the s-bond
selectivity of the reaction is not reversed by the enhance of
steric effect (from 3u to 3v). It should be noted that some 1,1-
dicyanocyclopropenes cannot be smoothly used in this
transformation even if the conditions were further optimized
(Figure 1). 2w, 2x, and 2aa were nearly quantitively reco-
vered using standard protocol, meanwhile, 1a underwent its
own decarboxylative allylation reaction.[7] It might be at-
tributed to the effect of large steric hindrance. The reaction
system containing 2y or 2z was messy, and we can only find
a few product signals in LC-MS.
Then, we investigated the scope of alkynyl moieties in
allyl propiolates (Figure 2a). Allyl phenylpropiolates with
either an electron-donating or electron-withdrawing group on
benzene ring, were able to react with 2a to offer the corres-
ponding products with the exclusive configuration in good to
excellent yields (3w–3ag). The reaction conditions were
compatible with alkyl, trifluoromethyl, fluoride, chloride,
bromide, cyano, nitro, and acetal groups at ortho-, meta-, and
para- position of the benzene ring. Furthermore, naphthyl and
hetero aromatic propiolates also can be used for the con-
struction of dienynes (3ah–3ak). Gratifyingly, allyl silyl-
propiolates can be used successfully in this transformation to
afford products with silyl groups that are easy to be derived
(3al, 3am). The slight decline of s-bond selectivity of these
two reactions might be attributed to the stronger nucleo-
philicity of silyl ethynyl moieties. Moreover, the scope of allyl
moieties in allyl propiolates was examined (Figure 2b). The
representative a-, b-, or g-substituted allyl propiolates also
can participate effortlessly in the transformation to synthesize
the corresponding alkynylallylation products in linear selec-
tivity (3an–3aq). And a series of allyl propiolates derived
from natural allyl alcohols, such as eraniol (3ar), nerol (3as),
perrilly alcohol (3at), farnesol (3au), phytol (3av), and sola-
nesol (3aw), were also successfully used in our method.
Besides, the reaction can be efficiently performed on
a gram scale with high turnover numbers (TONs) of the ca-
talyst (for details, see the Supporting Information, Tables S6,
S7). On the basis of standard protocol, the scale-up reaction
of 7.5 mmol of 1a with 5 mmol of 2a can be achieved only by
increasing concentration and prolonging time. With the de-
Figure 2. Scope of allyl propiolates. Unless otherwise noted, all reac-
tions were performed using 0.30 mmol 1 and 0.20 mmol 2a in 1 mL
MeCN at 608C for 18 h. Yield of isolated product. a) 808C, 36 h;
b) 808C, 24 h; c) 508C, 36 h; d) 5 mol% Pd2(dba)3, 30 mol% P(p-
CF3C6H4)3, 808C, 18 h.
crease of the amount of catalyst, the yield of the reaction
decreased slightly, but the TONs of the catalyst increased
greatly. Using 0.1 mol% catalyst, the reaction produced 1.52 g
of 3a, with the yield of 69% and the TONs being 345. Fur-
thermore, 0.1 mol% catalyst loading afforded 1.49 g of 3b,
with the isolated yield of 78% and the TONs being 390.
Next, the highly functionalized dienynes 3 provided by
this method can be further transformed with no trouble
(Figure 3). In order to take full advantage of the structural
characteristics of most products, that is, having two con-
trollable aryls on the same side of the tetrasubstituted alke-
nes, we made use of the air-driven oxidative photocyclization
developed by Watanabeꢀs group[11] for efficiently constructing
specific position functionalized phenanthrenes, which are not
easy to be obtained through other ways. With or without
substituents on its benzene rings, the compound 3 was able to
successfully participate in the oxidative cyclization (4a–4 f) to
offer a single product in good to excellent yield. It is worth
mentioning that the configuration of representative product
4a was determined by X-ray diffraction[16] and the reaction of
3q also exhibited satisfactory regioselectivity that was regu-
lated by steric effect. Moreover, the tert-butyl carboxylate
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Angew. Chem. 2020, 132, 2 – 9
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