Gold-catalyzed carbenoid transfer reactions of diynes - Pinacol rearrangement versus retro-Buchner reaction

Article abstract of DOI:10.1002/adsc.201400849

Aromatic diyne systems bearing one terminal propargylic acetate moiety and one tertiary propargylic alcohol subunit were converted in the presence of a gold catalyst. After an initial 1,2-migration of the acetoxy group at the terminal alkyne, a gold carbenoid is formed which is then transferred onto the internal alkyne of the propargylic alcohol. This combination enables the use of propargylic acetates as precursors for a gold-catalyzed pinacol-type rearrangement. In the final pinacol-like step the shift of an alkyl or aryl moiety onto an electrophilic gold carbenoid/cation terminates the reaction and 1-naphthyl ketones are obtained as products. If electron-rich aromatic backbones are used, a mechanistically interesting alternative pathway including a retro-Buchner reaction is opened.

Full text of DOI:10.1002/adsc.201400849

FULL PAPERS
DOI: 10.1002/adsc.201400849
Very Important Publication
Gold-Catalyzed Carbenoid Transfer Reactions of Diynes –
Pinacol Rearrangement versus Retro-Buchner Reaction
Tobias Lauterbach,a Takafumi Higuchi,a,b Matthias W. Hussong,a
Matthias Rudolph,a Frank Rominger,a Kazushi Mashima,b
and A. Stephen K. Hashmia,*
a
Organisch-Chemisches Institut, Ruprecht-Karls-Universitꢀt Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg,
Germany
Fax : (+49)-6221-54-4205; e-mail: hashmi@hashmi.de (homepage: http://www.hashmi.de)
Department of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
b
Received: August 27, 2014; Revised: November 19, 2014; Published online: && &&, 0000
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201400849.
Abstract: Aromatic diyne systems bearing one termi- an alkyl or aryl moiety onto an electrophilic gold car-
nal propargylic acetate moiety and one tertiary prop- benoid/cation terminates the reaction and 1-naphthyl
argylic alcohol subunit were converted in the pres- ketones are obtained as products. If electron-rich ar-
ence of a gold catalyst. After an initial 1,2-migration omatic backbones are used, a mechanistically inter-
of the acetoxy group at the terminal alkyne, a gold esting alternative pathway including a retro-Buchner
carbenoid is formed which is then transferred onto reaction is opened.
the internal alkyne of the propargylic alcohol. This
combination enables the use of propargylic acetates Keywords: carbenoid transfer; gold carbenoids;
as precursors for a gold-catalyzed pinacol-type rear- naphthalenes; pinacol rearrangement; retro-Buchner
rangement. In the final pinacol-like step the shift of reaction
Introduction
useful organic transformations following this reactivi-
ty principle have been developed.[1]
Among the key fundamental reactions in the field of
A valuable expansion of this methodology was dis-
gold catalysis, the generation of gold carbenoids via covered only recently by the groups of Hirao/Chan,
a 1,2-acyl migration of propargylic acetates plays an Oh and ourselves. If a second alkyne is offered in an
important role (Scheme 1, upper part). Due to the appropriate distance, a transfer of the carbenoid is
easy access to the starting materials combined with possible and further transformations with the newly
the diverse reactivity of the carbenoid centre, many generated vinyl gold carbenoids are possible
(Scheme 1, lower part).[2] Carbenoid transfer reactions
to an adjacent alkyne were also reported for gold car-
benoids derived either from diazo compounds[3] or
from N-oxides via intermolecular oxygen transfer.[4]
As a part of our studies concerning naphthyl gold
carbenoids generated via carbenoid transfer reactions,
we considered the possibility of a pinacol-type rear-
rangement as terminating step of the reaction cascade
(Scheme 2). Pinacol-like reactions are known in the
field of gold chemistry. So far the carbenoid inter-
mediates were generated by oxygen transfer from N-
oxides,[5] by an initial enyne cyclization,[6] or by the
generation of allyl cations from allylic alcohol deriva-
tives.[7] So far, no approaches using 1,2-acyl migrations
Scheme 1. Upper part: generation of gold carbenoids via 1,2-
have been reported, which is most probably based on
the fact that internal alkynes, which would serve as
acyl migration. Lower part: subsequent carbenoid transfer
via a pendant alkyne.
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1
ÞÞ
These are not the final page numbers!

FULL PAPERS
Tobias Lauterbach et al.
Table 1. Screening of the reaction conditions.
Scheme 2. Desired carbenoid shift/carbenoid transfer/pina-
col rearrangement cascade.
Entry [Au] [5 mol%] AgX [5 mol%] Solvent Yield[a]
1
PPh3AuNTf2
–
DCE
4%
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16[b]
17[c]
18[d]
19
20
PPh3AuNTf2
PPh3AuNTf2
PPh3AuNTf2
PPh3AuCl
PPh3AuCl
PPh3AuCl
PPh3AuCl
PPh3AuCl
AuCl
XPhosAuCl
SPhosAuCl
IPrAuCl
3
4
4
4
4
4
–
–
–
–
benzene 2%
toluene traces
precursors, are known to favour a competing allene
formation via 1,3-acyl migration instead of the forma-
tion of a gold carbenoid.[8] We envisioned that diynes
as starting materials would be ideal to circumvent this
intrinsic problem. By employing this strategy, one
could generate a gold carbenoid by a 1,2-acyl migra-
tion at one terminal alkyne, which can then be trans-
ferred by a carbenoid transfer onto a second internal
alkyne that bears a propargylic subunit which eventu-
ally is able to undergo a pinacol-like rearrangement
(Scheme 2).
MeCN
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
traces
traces
traces
18%
15%
traces
15%
15%
24%
23%
35%
60%
41%
40%
traces
–
AgNTf2
AgPF6
AgSbF6
AgBF4
AgOTf
–
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
–
Results and Discussion
For a screening of the reaction conditions we applied
diyne 1a which was available in three steps from 2-
bromobenzaldehyde via a Sonogashira coupling, an
addition of ethynylmagnesium bromide and an acyla-
tion. A first series of experiments with PPh3AuNTf2
in different solvents delivered only poor results
(Table 1, entries 1–5), no matter whether preactivated
or in situ generated catalysts were applied. A varia-
AgSbF6
–
[a]
Yield was determined by GCMS using hexamethylben-
zene as internal standard.
0.06M solution.
0.24M solution.
0.48M solution.
[b]
[c]
[d]
tion of the counterion at the gold catalyst gave a first both of these control experiments showed no conver-
improvement, but yields of about 15% with hexafluor- sion (entries 19 and 20). A competing oligomeriza-
oantimonate (entry 7) and with tetrafluoroborate tion/polymerization[11] is observed in all entries, ac-
(entry 8) were still unsatisfactory. Triflate gave only counting for the reduced yields. The reason for the su-
traces of product (entry 9). Simple gold chloride periority of the carbene complexes 3 and 4 is un-
(entry 10) and complexes bearing Buchwald-type li- known.[12]
gands (entries 11 and 12) showed only a minor im-
With the optimized conditions we evaluated the
provement with yields up to 24%. The same was the substrate scope. The results are summarized in
case with the frequently used IPr ligand (entry 13). Table 2. With test substrate 1a a yield of 54% of the
Slightly better results were obtained with unsaturated desired pinacol rearrangement product 2a could be
NHC complex 3 (entry 14).[9] By far the best results obtained (entry 1). A different picture was observed
were obtained by the use of nitrogen acyclic carbene with aromatic backbones containing electron-rich
(NAC) 4 (entry 15).[10] Attempts to further improve oxygen donors as substituents. With substrates 1b–1d
the yield by changing the concentration (entries 16– (entries 2–4) mixtures of two different compounds
18) failed. Finally, we tested the reaction with only were obtained. Unfortunately, the yields were unsatis-
a non-activated catalyst or with only the silver salt, factory for these substrates. Besides the expected pi-
2
asc.wiley-vch.de
ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
These are not the final page numbers!

FULL PAPERS
Gold-Catalyzed Carbenoid Transfer Reactions of Diynes
Table 2. Scope of the reaction.
Table 2. (Continued)
[a]
A mixture of the desired product (dp) and inseparable
by-product (bp) was obtained
nacol-type product, a second product was obtained in the by-products two carbon atoms are missing and the
significant amounts. Mass spectrometry revealed that acyl group is directly attached to the naphthalene
a formal ethene elimination leads to this by-product. system. A methyl substitution at the aromatic back-
NMR analysis of the compounds together with the re- bone selectively delivered the pinacol product in
sults of a X-ray crystal structure analysis allowed moderate yields (entry 5). Electron-deficient fluorine
a safe structural assignment (Figure 1).[13] For all of substituents were also tolerated, but yields were sig-
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
3
ÞÞ
These are not the final page numbers!

FULL PAPERS
Tobias Lauterbach et al.
rangement product. Coordination of the cationic gold
catalyst to the cyclopropene double bond delivers sta-
bilized benzylic cation V, which under aromatization
delivers naphthyl carbenoid VI. Finally, the reaction
is terminated by an alkyl migration onto the electro-
philic carbenoid carbon which delivers the desired
products dp-2. Pathways B and C provide possible ex-
planations for the formation of by-product bp-2. In
the case of path B the gold catalyst adds to the oppo-
site end of the cyclopropene double bond and the ho-
moallyl cation VII is formed. Ring opening of the cy-
clopropyl unit then delivers gold carbenoid IXa/
b which can also be regarded as a gold-stabilized tro-
pylium cation. Pathway C would also lead to the
same intermediate IXa/b, but breaking of the aromat-
ic system under formation of bent allene VIII and
subsequent addition to the cationic gold complex
Figure 1. Solid state molecular structure of the by-product
bp-2c.
nificantly lower (entries 6 and 7). Next we investigat- should be less favoured. The final sequence of both
ed different substitution patterns at the propargylic pathways B and C is initiated via an alkyl migration[16]
position. With mixed aromatic/aliphatic tertiary alco- onto the carbenoid carbon atom followed by a retro-
hol 1h as the starting material, a selective migration Buchner reaction[17] from norcaradiene XI that is in
of the phenyl group took place delivering product 2h equilibrium with cycloheptatriene X. Finally, by-prod-
in moderate yield. Two phenyl groups in propargylic uct bp-2 is formed under release of ethene and the
positions were also tolerated and product 2i was ob- gold catalyst.
tained in comparable yield (54%) to the correspond-
ing methyl-substituted substrate 2a. Finally, we inves-
tigated the possibility of a ring expansion reaction. Conclusions
Fortunately both five- and six-membered ring systems
could be converted leading to the corresponding six- In conclusion, we have presented the first example of
and seven-membered products in yields of 41% (2j) a gold-catalyzed pinacol-type reaction that is based
and 62% (2k). The solid state molecular structure of on a 1,2-acetoxy migration as initiating step. By the
2k, obtained by another X-ray crystal structure analy- use of diyne systems the gold carbenoid can be gener-
sis, nicely confirms the constitution of the ring expan- ated at one terminal alkyne (which is crucial for the
sion product obtained (Figure 2).[13]
formation of a gold carbenoid) and can then be trans-
A plausible mechanistic picture[14] for the formation ferred onto a second internal alkyne. This pendant ter-
of the two products is depicted in Scheme 3. The reac- tiary propargyl alcohol subunit enables the pinacol re-
tion cascade is initiated via the known 1,2-acyl migra- arrangement. In dependency of the substitution pat-
tion that delivers carbenoid III as intermediate. A tern of the aromatic backbone an alternative retro-
subsequent cyclopropenation delivers key intermedi- Buchner reaction can take place under elimination of
ate IV.[15] The ring opening of the so formed cyclopro- ethene.
pene then determines the product selectivity. Path A
describes the formation of the desired pinacol rear-
Experimental Section
4-(2-Oxo-1,2-diphenylethyl)naphthalen-2-yl Acetate
(2i)
120 mg (315 mmol) of 1i were dissolved in 2.6 mL of DCE.
6.13 mg (15.8 mmol) of NACAuCl (4) and 5.42 mg
(15.8 mmol) of AgSbF6 were added and the mixture was
stirred at 808C for 18 h. After this time the solvent was re-
moved under reduced pressure and the crude product was
purified by column chromatography (SiO2, PE:EA, 10:1) to
afford 2i as a brown solid; yield: 65.0 mg (171 mmol, 54%).
1
Rf (PE:EA=5:1)=0.08; H NMR (500 MHz, C6D6): d=1.59
(s, 3H), 6.72 (s, 1H), 6.89 (t, J=7.5 Hz, 2H), 6.95–7.00 (m,
2H), 7.05 (t, J=7.6 Hz, 2H), 7.12–7.14 (m, 1H), 7.17–7.18
(m, 1H), 7.25 (d, J=7.5 Hz, 2H), 7.37 (d, J=2.3 Hz, 1H),
Figure 2. Solid state molecular structure of 2j.
4
asc.wiley-vch.de
ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
These are not the final page numbers!

FULL PAPERS
Gold-Catalyzed Carbenoid Transfer Reactions of Diynes
Scheme 3. Mechanistic proposal for the formation of the ethene elimination products.
7.50–7.52 (m, 2H), 7.98–8.01 (m, 3H); 13C NMR (125 MHz,
4-(2-Oxocycloheptyl)naphthalen-2-yl Acetate (2k)
C6D6): d=20.5 (q), 56.3 (q), 60.1 (d), 119.0 (d), 123.3 (d),
126.5 (d), 126.7 (d), 127.6 (d), 128.9 (d, 2C), 129.1 (d, 2C),
129.1 (d, 2C), 129.3 (d), 130.1 (d, 2C), 133.1 (d), 133.1 (d),
135.2 (s), 137.1 (s), 138.2 (s), 138.2 (s), 148.7 (s), 168.4 (s),
197.4 (s); IR (film): n=3062, 2933, 1759, 1682, 1625, 1598,
1581, 1512, 1495, 1448, 1431, 1394, 1367, 1294, 1271, 1200,
1131, 1078, 1032, 1013, 912, 887, 845, 800, 774, 745, 726, 696,
657, 626 cmÀ1; HR -MS [DART (+)]: m/z=398.1770, calcd.
for [C26H24O3N]+, [M+NH4]+: 398.1756.
120 mg (405 mmol) of 1k were dissolved in 3.40 mL of DCE.
7.87 mg (20.3 mmol) of NACAuCl and 6.96 mg (20.3 mmol)
of AgSbF6 were added and the mixture was stirred at 808C
for 16 h. After this time the solvent was removed under re-
duced pressure and the crude product was purified by
column chromatography (SiO2, PE:EA, 10:1) to afford 2k as
an orange oil; yield: 74.0 mg (250 mmol, 62%). Rf (PE:EA=
5:1)=0.09; 1H NMR (400 MHz, CDCl3): d=1.46–1.65 (m,
3H), 1.76–1.86 (m, 1H), 2.02- 2.14 (m, 3H), 2.24–2.31 (m,
1H), 2.35 (s, 3H), 2.66–2.73 (m, 1H), 2.76–2.83 (m, 1H),
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
5
ÞÞ
These are not the final page numbers!

FULL PAPERS
Tobias Lauterbach et al.
4.58 (dd, J=11.1 Hz, J=3.5 Hz, 1H),7.18 (d, J=2.3 Hz,
1H), 7.47–7.51 (m, 3H), 7.79–7.81 (m, 1H), 7.97–7.99 (m,
1H); 13C NMR (100 MHz, CDCl3): d=21.4 (q), 25.2 (t), 29.4
(t), 29.9 (t), 32.1 (t), 43.3 (t), 53.7 (d), 118.0 (d), 120.5 (d),
123.6 (d), 126.1 (d), 126.5 (d), 128.9 (d), 129.9 (s), 134.5 (s),
139.4 (s), 148.0 (s), 169.9 (s), 213.0 (s); IR (film): n=3503,
3066, 2391, 2856, 1768, 1705, 1625, 1602, 1582, 1512, 1454,
1432, 1392, 1369, 1344, 1315, 1218, 1169, 1150, 1131, 1014,
983, 934, 915, 889, 843, 799, 773, 745 cmÀ1; HR-MS [DART
[3] a) C. A. Witham, P. Mauleon, N. D. Shapiro, B. D.
Sherry, F. D. Toste, J. Am. Chem. Soc. 2007, 129, 5838–
5839; for related rhodium-catalyzed processes see also:
b) A. Padwa, Molecules 2001, 6, 1–12.
[4] P. Nçsel, L. N. dos Santos Comprido, T. Lauterbach, M.
Rudolph, F. Rominger, A. S. K. Hashmi, J. Am. Chem.
Soc. 2013, 135, 15662–15666.
[5] a) G. Li, L. Zhang, Angew. Chem. 2007, 119, 5248–
5251; Angew. Chem. Int. Ed. 2007, 46, 5156–5159; for
+
(+)]: m/z=314.1759, calcd. for [C18H22O3N]+, [M+NH4 ]:
a
related redox–pinacol–Mannich cascade reaction
314.1756.
using a nitrone as oxygen donor see also: b) H. S.
Yeom, Y. Lee, J. Jeong, E. So, S. Hwang, J. E. Lee, S. S.
Lee, S. Shin, Angew. Chem. 2010, 122, 1655–1658;
Angew. Chem. Int. Ed. 2010, 49, 1611–1614.
Acknowledgements
[6] a) J.-M. Tang, S. Bhunia, S. M. A. Sohel, M.-Y. Lin, H.-
Y. Liao, S. Datta, A. Das, R.-S. Liu, J. Am. Chem. Soc.
2007, 129, 15677–15683; b) S. F. Kirsch, J. T. Binder, B.
Crone, A. Duschek, T. T. Haug, C. Liebert, H. Menz,
Angew. Chem. 2007, 119, 2360–2363; Angew. Chem.
Int. Ed. 2007, 46, 2310–2313; c) B. Baskar, H. J. Bae,
S. E. An, J. Y. Cheong, Y. H. Rhee, A. Duschek, S. F.
Kirsch, Org. Lett. 2008, 10, 2605–2607; d) H. Menz, J. T.
Binder, B. Crone, A. Duschek, T. T. Haug, S. F. Kirsch,
P. Klahn, C. Liꢃbert, Tetrahedron 2009, 65, 1880–1888.
[7] L. L. Zhu, X.-X. Li, W. Zhou, X. Li, Z. Chen, J. Org.
Chem. 2011, 76, 8814–8823.
[8] a) N. Marion, S. P. Nolan, Angew. Chem. 2007, 119,
2806–2809; Angew. Chem. Int. Ed. 2007, 46, 2750–2752;
for further references, see: b) J. Zhao, C. O. Hughes,
F. D. Toste, J. Am. Chem. Soc. 2006, 128, 7436–7437;
c) C. H. Oh, A. Kim, New J. Chem. 2007, 31, 1719–
1721; d) T. Luo, S. L. Schreiber, Angew. Chem. 2007,
119, 8398–8401; Angew. Chem. Int. Ed. 2007, 46, 8250–
8253; e) T. Luo, S. L. Schreiber, J. Am. Chem. Soc.
2009, 131, 5667–5674; f) D.-H. Zhang, L.-F. Yao, Y.
Wei, M. Shi, Angew. Chem. 2011, 123, 2631–2635;
Angew. Chem. Int. Ed. 2011, 50, 2583–2587; g) D.
Lebœuf, A. Simonneau, C. Aubert, M. Malacria, V.
Gandon, L. Fensterbank, Angew. Chem. 2011, 123,
7000–7003; Angew. Chem. Int. Ed. 2011, 50, 6868–6871;
h) W. Rao, M. J. Koh, P. Kothandaraman, P. W. H.
Chan, J. Am. Chem. Soc. 2012, 134, 10811–10814; i) Y.
Yu, W. Yang, F. Rominger, A. S. K. Hashmi, Angew.
Chem. 2013, 125, 7735–7738; Angew. Chem. Int. Ed.
2013, 52, 7586–7689; j) A. S. K. Hashmi, W. Yang, Y.
Yu, M. M. Hansmann, M. Rudolph, F. Rominger,
Angew. Chem. 2013, 125, 1368–1371; Angew. Chem. Int.
Ed. 2013, 52, 1329–1332.
H.T. is grateful for support by the “Engineering Science Stu-
dent Dispatch Program” of the Graduate School of Engineer-
ing Science, Osaka University. Gold salts were generously do-
nated by Umicore AG & Co. KG.
References
[1] For selected publications, see: a) K. Miki, K. Ohe, S.
Uemura, Tetrahedron Lett. 2003, 44, 2019–2022; b) K.
Miki, K. Ohe, S. Uemura, J. Org. Chem. 2003, 68,
8505–8513; c) A. Fꢂrstner, P. Hannen, Chem. Commun.
2004, 2546–2547; d) A. Fꢂrstner, P. Hannen, Chem.
Eur. J. 2006, 12, 3006–3019; e) M. J. Johansson, D. J.
Gorin, S. T. Staben, F. D. Toste, J. Am. Chem. Soc.
2005, 127, 18002–18003; f) N. Marion, S. P. Nolan,
Angew. Chem. 2007, 119, 2806–2809; Angew. Chem.
Int. Ed. 2007, 46, 2750–2752; g) D. J. Gorin, I. D. G.
Watson, F. D. Toste, J. Am. Chem. Soc. 2008, 130, 3736–
3737; h) A. Correa, N. Marion, L. Fensterbank, M.
Malacria, S. P. Nolan, L. Cavallo, Angew. Chem. 2008,
120, 730–733; Angew. Chem. Int. Ed. 2008, 47, 718–721;
i) G. Li, G. Zhang, L. Zhang, J. Am. Chem. Soc. 2008,
130, 3740–3741; j) Y. Wang, B. Lu, L. Zhang, Chem.
Commun. 2010, 46, 9179–9181; k) C. A. Sperger, J. E.
Tungen, A. Fiksdahl, Eur. J. Org. Chem. 2011, 3719–
3722; l) E. Rettenmeier, A. M. Schuster, M. Rudolph,
F. Rominger, C. A. Gade, A. S. K. Hashmi, Angew.
Chem. 2013, 125, 5993–5997; Angew. Chem. Int. Ed.
2013, 52, 5880–5884; m) C. H. Oh, J. H. Kim, B. K. Oh,
J. R. Park, J. H. Lee, Chem. Eur. J. 2013, 19, 2592–2596;
n) W. Rao, P. W. H. Chan, Chem. Eur. J. 2014, 20, 713–
718; for reviews, see: o) A. S. K. Hashmi, G. J. Hutch-
ings, Angew. Chem. 2006, 118, 8064–8105; Angew.
Chem. Int. Ed. 2006, 45, 7896–7936; p) D. Garayalde,
C. Nevado, Beilstein J. Org. Chem. 2011, 7, 767–780;
q) R. K. Shiroodi, V. Gevorgyan, Chem. Soc. Rev. 2013,
42, 4991–5001.
[9] a) A. S. K. Hashmi, C. Lothschꢂtz (BASF SE), WO
Patent, WO 2012/056419A1, 2012; for the benefits of
carbene ligands in gold catalysis, see: b) D. Gatineau,
J.-P. Goddard, V. Mouriꢄs-Mansuy, L. Fensterbank, Isr.
J. Chem. 2013, 53, 892–900; c) M. C. Blanco Jaimes,
C. R. N. Bçhling, J. M. Serrano-Becerra, A. S. K.
Hashmi, Angew. Chem. 2013, 125, 8121–8124; Angew.
Chem. Int. Ed. 2013, 52, 7963–7966.
[2] a) W. Rao, M. J. Koh, D. Li, H. Hirao, P. W. Chan, J.
Am. Chem. Soc. 2013, 135, 7926–7932; b) C. H. Oh,
J. H. Kim, L. Piao, J. Yu, S. Y. Kim, Chem. Eur. J. 2013,
19, 10501–10505; c) T. Lauterbach, S. Gatzweiler, P.
Nçsel, M. Rudolph, F. Rominger, A. S. K. Hashmi,
Adv. Synth. Catal. 2013, 355, 2481–2487; d) T. Lauter-
bach, M. Ganschow, M. W. Hussong, M. Rudolph, F.
Rominger, A. S. K. Hashmi, Adv. Synth. Catal. 2014,
356, 680–686.
[10] A. S. K. Hashmi, T. Hengst, C. Lothschꢂtz, F. Roming-
er, Adv. Synth. Catal. 2010, 352, 1315–1337.
[11] For a recent report on gold-catalyzed polymerization
reactions, see: A. S. K. Hashmi, S. Schꢀfer, V. Gçker,
C. D. Eisenbach, K. Dirnberger, Z. Zhao-Karger, P.
6
asc.wiley-vch.de
ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
These are not the final page numbers!

FULL PAPERS
Gold-Catalyzed Carbenoid Transfer Reactions of Diynes
Crewdson, Aust. J. Chem. 2014, 67, 500–506, and refer-
ences cited therein.
[16] Concerted thermal 1,3-shifts require an antarafacial re-
action at the migrating component, which might ex-
plain why the side product bp-2 is only observed with
alkyl but not with aryl groups (the latter would possess
a higher migratory aptitude for sequential 1,2-shifts):
a) B. Miller, Advanced Organic Chemistry, 2nd edn.,
Pearson Prentice Hall, Upper Saddle River, 2004. As
in general for Wagner–Meerwein rearrangements, the
phenyl migration is preferred over a methyl migration
also in gold catalysis, see: b) E. Benedetti, G. Lemiꢄre,
L.-L. Chapellet, A. Penoni, G. Palmisano, M. Malacria,
J.-P. Goddard, L. Fensterbank, Org. Lett. 2010, 12,
4396–4399; c) A. S. Dudnik, A. W. Sromek, M. Rubina,
J. T. Kim, A. V. Kel’in, V. Gevorgyan, J. Am. Chem.
Soc. 2008, 130, 1440–1452.
[12] In general, the most active gold(I) catalysts described
so far bear carbene ligands: a) M. C. Blanco Jaimes,
C. R. N. Bçhling, J. M. Serrano-Becerra, A. S. K.
Hashmi, Angew. Chem. 2013, 125, 8121–8124; Angew.
Chem. Int. Ed. 2013, 52, 7963–7966; these have proven
to be superior to bulky phosphates: b) M. C. Blanco
Jaimes, F. Rominger, M. M. Pereira, R. M. B. Carrilho,
S. A. C. Carabineiro, A. S. K. Hashmi, Chem. Commun.
2014, 50, 4937–4940.
[13] CCDC 1011516 (bp-2c) and CCDC 1011517 (2j) con-
tain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
[17] For a gold-catalyzed retro-Buchner reaction, see also:
a) C. R. Solorio-Alvarado, A. M. Echavarren, J. Am.
Chem. Soc. 2010, 132, 11881–11883; b) C. R. Solorio-
Alvarado, Y. Wang, A. M. Echavarren, J. Am. Chem.
Soc. 2011, 133, 11952–11955.
[14] A. S. K. Hashmi, Angew. Chem. 2010, 122, 5360–5369;
Angew. Chem. Int. Ed. 2010, 49, 5232–5241.
[15] For a gold-catalyzed cyclopropenation see also: J. F.
Briones, H. M. Davies, J. Am. Chem. Soc. 2012, 134,
11916–11919.
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
7
ÞÞ
These are not the final page numbers!

FULL PAPERS
8 Gold-Catalyzed Carbenoid Transfer Reactions of Diynes –
Pinacol Rearrangement versus Retro-Buchner Reaction
Adv. Synth. Catal. 2015, 357, 1 – 8
Tobias Lauterbach, Takafumi Higuchi,
Matthias W. Hussong, Matthias Rudolph, Frank Rominger,
Kazushi Mashima, A. Stephen K. Hashmi*
8
asc.wiley-vch.de
ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
These are not the final page numbers!