Direct synthesis of 1,4-diols from alkenes by iron-catalyzed aerobic hydration and C-H hydroxylation

Article abstract of DOI:10.1002/anie.201308675

Various 1,4-diols are easily accessible from alkenes through iron-catalyzed aerobic hydration. The reaction system consists of a user-friendly iron phthalocyanine complex, sodium borohydride, and molecular oxygen. Furthermore, the effect of additional ligands on the iron complex was examined for a model reaction. The second hydroxy group is installed by direct C(sp³)-H oxygenation, which is based on a [1,5] hydrogen shift process of a transient alkoxy radical that is formed by formal hydration of the olefin. One more hydroxy group: A method for the synthesis of 1,4-diols from simple alkenes has been developed. This unusual transformation entails an iron-catalyzed aerobic hydration and is achieved with convenient reagents, such as molecular oxygen. The formation of an intermediary alkoxy radical, which undergoes a [1,5] hydrogen shift, is likely to be essential for C(sp³)-H hydroxylation. Pc=phthalocyanine.

Full text of DOI:10.1002/anie.201308675

.
Angewandte
Communications
DOI: 10.1002/anie.201308675
Synthetic Methods
Direct Synthesis of 1,4-Diols from Alkenes by Iron-Catalyzed Aerobic
À
Hydration and C H Hydroxylation**
Takuma Hashimoto, Daisuke Hirose, and Tsuyoshi Taniguchi*
Abstract: Various 1,4-diols are easily accessible from alkenes
through iron-catalyzed aerobic hydration. The reaction system
consists of a user-friendly iron phthalocyanine complex,
sodium borohydride, and molecular oxygen. Furthermore,
the effect of additional ligands on the iron complex was
and hydration of alkenes are powerful transformations for the
preparation of monoalcohols, and these methods complement
each other in terms of regioselectivity.[1,2] A hydroformula-
tion–reduction process of alkenes is a new concept for the
synthesis of terminal alcohols.[3] Selenium dioxide is often
used for selective allylic hydroxylation.[2,4] An osmium tetr-
oxide mediated 1,2-dihydroxylation reaction of alkenes is
a reliable method to obtain cis-configured 1,2-diols.[1,5,6] In
connection with this reaction, epoxidation of alkenes fol-
lowed by hydration is used to prepare trans-1,2-diols.[1] 1,3- or
1,4-diols are compounds that are synthetically as important as
1,2-diols.[7] Although methods for the direct synthesis of 1,3-
diols from alkenes have not been established,[8] they can be
easily prepared by stepwise methods, for example, by
combining an aldol reaction with a reduction process. In
contrast, efficient methods that provide short synthetic routes
to 1,4-diols have hardly been reported.[9] Therefore, direct
dihydroxylation methods for the synthesis of 1,4-diols from
simple alkenes are valuable.[10] Herein, we describe the direct
examined for a model reaction. The second hydroxy group is
3
À
installed by direct C(sp ) H oxygenation, which is based on
a [1,5] hydrogen shift process of a transient alkoxy radical that
is formed by formal hydration of the olefin.
T
he development of synthetic methods for introducing
hydroxy groups into organic molecules is a fundamental
task in organic chemistry because hydroxy groups exist in
many useful organic compounds, such as biologically active
products and industrial materials.[1] In general, alkenes are
chosen as precursors for alcohols because numerous reliable
methods for introducing hydroxy groups into alkenes have
been established (Scheme 1).[1] For instance, hydroboration
1,4-dihydroxylation of aliphatic alkenes by an iron-catalyzed
3
À
aerobic formal hydration of olefins and C(sp ) H oxidation.
À
Oxygenation of unactivated C H bonds has been one of
the main subjects in organic chemistry over the past
century.[11] The direct hydroxylation of unactivated
3
[12]
À
C(sp ) H bonds is a synthetically attractive method.
A
number of stoichiometric or catalytic methods for the
hydroxylation of hydrocarbons using oxygen sources such as
peroxides or hypervalent iodine compounds have been
À
reported, and secondary or tertiary C H bonds are predom-
inantly oxidized to produce secondary or tertiary alcohols via
cationic or radical intermediates.[11] In contrast, the direct
À
hydroxylation of methyl C H bonds is rare, but transition-
metal catalysts that can activate the methyl group enable this
transformation with the aid of effective directing
groups.[11,12d,e] Some remote functionalization reactions with
Scheme 1. Methods for the hydroxylation of alkenes.
À
free radicals can also be described as directed C H function-
alizations because they often involve an intramolecular
hydrogen shift of a highly reactive radical species; in a
[*] T. Hashimoto, Dr. T. Taniguchi
3
À
School of Pharmaceutical Sciences
Institute of Medical, Pharmaceutical and Health Sciences
Kanazawa University
Kakuma-machi, Kanazawa 920-1192 (Japan)
E-mail: tsuyoshi@p.kanazawa-u.ac.jp
C(sp ) H functionalization, this is typically a [1,5] hydrogen
shift.[13]
Iron-catalyzed redox hydration reactions of alkenes with
hydride reagents and molecular oxygen represent a mild
method to introduce a hydroxy group.[14] Radical species
presumably participate in the mechanism, and extensions of
this reaction to advanced chemical transformations were
D. Hirose
Graduate School of Natural Science and Technology
Kanazawa University
Kakuma-machi, Kanazawa 920-1192 (Japan)
recently reported.[14c–f] In the course of another investigation
3
À
of these types of reactions, we noticed that remote C(sp ) H
[**] This work was partially supported by JSPS KAKENHI (23790008 and
25460011).
oxygenation can occur alongside hydration of an olefin. This
observation has been overlooked thus far, and therefore, we
designed an experiment using simple alkene 1a to reveal the
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201308675.
2730
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2014, 53, 2730 –2734

Angewandte
Chemie
details of this reaction. Treatment of alkene 1a with a catalytic
amount (10 mol%) of iron phthalocyanine [Fe(Pc)] and
sodium borohydride (NaBH4; 1.5 equiv) under an oxygen
atmosphere in ethanol (0.1m) gave 1,4-diol 2a in 26% yield
(Scheme 2).[15] Although the yield of 1,4-diol 2a was not
adequate at that point, it was clear that this reaction had the
following unique and advantageous characteristics: 1) This
Indeed, F was detected by GC-MS analysis as the main by-
product of the reaction shown in Scheme 2.[17] On the other
hand, highly reactive alkoxy radical D would undergo
a [1,5] hydrogen shift to provide alkyl radical intermediate E.
This process was supported by a ring-opening reaction of the
radical clock substrate 2-methyl-5-(trans-2-phenylcyclo-
propyl)-2-pentene.[18] Finally, 1,4-diol 2a would be obtained
through a pathway that is similar to that for the formation of
complex C from alkyl radical B.[18]
As described above, competitive formation of monoalco-
hol F was likely to result in a diminished yield of diol 2a. We
examined various reaction conditions (catalysts, hydride
sources, amount of reagents, solvents, temperature, etc.) to
improve the yield of diol 2a, but none of the attempts led to
any improvements.[18] Next, we focused on the pathway to
generate alkoxy radical D and compound F from iron perox-
ide intermediate C. Nam and co-workers reported that the
destiny of iron porphyrin peroxide complexes is strongly
influenced by the axial ligands on the iron center.[19] In the
presence of weak electron donors, such as triflate or
Scheme 2. A preliminary experiment on 1,4-dihydroxylation. Yield
based on isolated product.
reaction is the first example of a synthesis of 1,4-diols from
a simple alkene in one step. 2) Reagents such as iron
phthalocyanine and sodium borohydride are inexpensive
and convenient, and the use of molecular oxygen as the
oxygen source is ideal from economic and environmental
viewpoints.[16]
À
perchlorate ions, heterolytic cleavage of the O O bond of
the iron peroxide complex is preferred over homolytic
cleavage and leads to the corresponding alkoxide and an
oxoiron(IV) cation radical intermediate. On the other hand,
strong electron donors, such as alkoxides or a chloride ion,
À
We intended to determine how the yield for the synthesis
of 1,4-diol 2a could be improved by elucidating the reaction
mechanism. A putative iron(III) hydride complex, which is
generated from iron phthalocyanine and sodium borohydride
in the presence of oxygen, might set off the reaction with 1a to
give adduct A (Scheme 3).[14] The reaction of organoiron
complex A with oxygen would generate tertiary-carbon-
centered radical B, which is followed by formation of iron
promote the homolytic cleavage of the O O bond to provide
the corresponding alkoxy radical and the oxoiron(IV) com-
plex. Therefore, we hypothesized that the addition of
a strongly electron-donating ligand to the reaction system
might increase the amount of alkoxy radical D, which may
then undergo a [1,5] hydrogen shift.
The results of reactions with various additives are shown
in Table 1.[18] As the chloride anion is a strong electron donor,
a modest, but clear improvement of the yield of diol 2a was
observed when the reaction was conducted in the presence of
lithium chloride (20 mol%; entry 2). In contrast, the addition
Table 1: The effect of additives on the transformation.[a]
Entry
Catalyst
Additive
Yield[b] [%]
1
2
3
4
5
6
7
8
[Fe(Pc)]
[Fe(Pc)]
[Fe(Pc)]
[Fe(Pc)]
[Fe(Pc)]
[Fe(Pc)]
[Fe(Pc)]
[Fe(Pc)]
[Fe(Pc)]
[Mn(Pc)]
[Fe(Tpp)Cl]
–
LiCl
26
44
20
41
38
29
38
45
LiClO4
NaOMe
KOAc
imidazole
1-methylimidazole
DMSO
Me2S
Scheme 3. Mechanistic proposal.
peroxide complex C. The formation of radical B was sup-
ported by mechanistic experiments, which included cycliza-
tion reactions of 1,6-dienes[14d] and trapping with 2,2,6,6-
tetramethylpiperidine 1-oxyl (TEMPO).[18] Alkoxy radical
intermediate D would be formed by cleavage of the weak
9
10
11
48 (43)[c]
48
51
Me2S
Me2S
[a] Reaction conditions: 1a (0.8 mmol), catalyst (0.08 mmol), NaBH4
(1.2 mmol), additive (0.16 mmol), EtOH (8 mL), O2 atmosphere
(1 atm), 2 h, room temperature. [b] Yield of isolated 2a. [c] [Fe(Pc)]
(5 mol%). DMSO=dimethylsulfoxide, Tpp=tetraphenylporphyrin.
O O bond of complex C.[15] If the reaction was terminated at
À
intermediate C by heterolytic bond cleavage or reduction,
monoalcohol F should be formed as the hydration product.
Angew. Chem. Int. Ed. 2014, 53, 2730 –2734
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
2731

.
Angewandte
Communications
Scheme 4. Synthesis of 1,4-diols from various alkenes. Reaction conditions: Alkene (0.8 mmol), NaBH4 (1.2 mmol), [Fe(Pc)] (0.08 mmol), Me2S
(0.16 mmol), EtOH (8 mL), O2 atmosphere (1 atm), 2–7 h, room temperature. Yields are based on isolated products. [a] NaBH4 was added in six
portions of 0.2 mmol (0.25 equiv) with intervals of 30 min, and the mixture was stirred for further 11 h. [b] A mixture of two diastereomers was
obtained. Ratios were estimated by 1H NMR analysis: 2e (60:40), 2k (50:50), 2m (50:50), 2n (50:50), 2o (50:50), 2r (50:50), 2s (70:30), 2t
1
(50:50), 2t’ (50:50), 2u (50:50). [c] 0.2 mmol scale. [d] NaBH4 (2.0 equiv; 1.6 mmol). [e] Estimated by H NMR analysis. TBDPS=tert-
butyldiphenylsilyl, Ts=p-toluenesulfonyl.
of lithium perchlorate did not improve the yield of 2a, as the
perchlorate anion only weakly coordinates to the iron
complex (entry 3). Similarly, an alkoxy or an acetate ligand
worked favorably in the present reaction (entries 4 and 5).
This trend is consistent with a report by Nam and co-workers.
Encouraged by these results, we examined the use of
imidazole and 1-methylimidazole, which are strongly donat-
ing amine ligands, but the yields did not improve (entries 6
and 7). On the other hand, sulfur compounds, such as
dimethyl sulfoxide and dimethyl sulfide, worked very well,
and good yields and reproducibility were observed.[20]
Dimethyl sulfide provided the best yield, and its removal is
easy because of its volatility. After we tested further additives,
such as other halogen, nitrogen, sulfur, phosphine, and
carbene compounds,[18] we concluded that the conditions
shown in entry 9 are the most suitable for the present
reaction, despite the foul smell of the small amount of
dimethyl sulfide. Manganese phthalocyanine or iron tetra-
phenylporphyrin chloride were similarly effective catalysts as
iron phthalocyanine (entries 10 and 11), but iron phthalocya-
nine seemed to be the most suitable catalyst in terms of
practicality.[21] These results confirmed the previously sug-
gested effects that axial ligands exert on the iron peroxide
complex.
Subsequently, we applied the optimized reaction condi-
tions to several alkenes (Scheme 4). A significant difference
in yield was observed for the reactions of branched alkene 1a
and linear alkene 1b to yield 1,4-diols 2a and 2b, respectively.
This observation clearly indicates that an entropic effect is
À
predominant in the C H oxygenation process. On the other
hand, the reaction of the more substituted alkene 1c was
somewhat sluggish, and a different procedure was needed to
drive the reaction to completion. Furthermore, diol 2c was
isolated in a lower yield than the product of the reaction with
À
1a. This result suggests that the C H oxygenation process
passes through a six-membered transition state D; an unfav-
orable 1,3-diaxial repulsion exists between the two axial
methyl groups in the transition state from alkene 1c. Another
limitation of the present reaction was revealed by the reaction
of the simple terminal alkene 1d, as diol 2d was isolated in
2732
www.angewandte.org
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2014, 53, 2730 –2734

Angewandte
Chemie
low yield. As the corresponding monoalcohol was formed as
the major product of this reaction, tertiary peroxide inter-
mediate C is likely to be an intermediate for the formation of
alkoxy radical D. Other 1,4-diols (2e–g) were obtained in
reactions. When 2-(2-methylphenyl)propene (1aa) was
employed as the substrate, the expected diol 2aa was isolated
along with a small amount of hemiacetal derivative 2aa’ (a
similar derivative was also observed for the reaction of 1u),
À
À
moderate to good yields by C H oxygenation of the methyl
but the combined yield of the C H oxygenation products was
À
groups of alkenes 1e–g. For alkenes 1h–u, C H oxygenation
high. Thus, we succeeded in demonstrating that this reaction
is a simple and reliable method to obtain various 1,4-diols
from alkenes. As mentioned above (Scheme 3), the corre-
sponding monoalcohols were the main by-products (ca. 20–
50%) of the present reaction. Furthermore, the formation of
small amounts of other by-products revealed that b-scission
reactions of the tertiary alkoxy radicals occurred for several
substrates.[23] It is difficult to avoid these side reactions at
present. As a tentative solution, we showed that a representa-
tive monoalcohol could be easily recycled by its transforma-
tion into the corresponding alkene by acid-catalyzed elimi-
nation.[18]
occurred on methylene carbon atoms to give diols 2h–u,
which entail secondary hydroxy groups. Interestingly, linear
alkenes, such as 1h and 1i, were suitable substrates and
provided the corresponding diols (2h and 2i) in reasonable
yields, whereas alkene 1b did not. Internal alkene 1j also
À
underwent aerobic hydration and C H oxygenation to afford
the corresponding diol 2j.
Many functional groups were tolerated under the present
reaction conditions. For instance, when the reaction of 1a was
performed in the presence of 3-iodoanisole, 1-bromodode-
cane, ethyl benzoate, or nitrobenzene, these additives
remained intact.[18] The recovery (> 90%) of the organo-
halides might indicate that the reaction does not proceed
through an electron transfer process.[14 g] Furthermore, the 1,4-
diols 2l–q were obtained from the reactions of the corre-
sponding alkenes 1l–q, which bear various functional groups.
Whereas carbon–carbon double bonds generally reacted with
the hydride, carbon–heteroatom multiple bonds, such as an
azide or a nitrile, remained intact. In the reaction of 1r, which
In conclusion, we have developed a unique 1,4-hydroxyl-
3
À
ation reaction of aliphatic alkenes that involves C(sp ) H
oxygenation. This reaction enabled oxidation of all types of
C(sp ) H bonds (methyl/primary, methylene/secondary, and
3
À
tertiary carbon centers) and allowed us to obtain various 1,4-
diols from simple alkenes using nontoxic and inexpensive
reagents under mild conditions. Molecular oxygen is the
source for the two oxygen atoms of the 1,4-diols. Experimen-
tal results suggest that a [1,5] hydrogen shift of a radical
species occurs as part of the reaction mechanism, and the
addition of ligands that strongly coordinate to the iron
peroxide intermediate seems to be important to improve the
yields for many substrates. This transformation of aliphatic
alkenes may be compared to the oxidative metabolism of
hydrocarbons by heme iron complexes and molecular
oxygen.[24] Our novel approach for the transformation of
simple molecules into functionalized compounds shows that
an advanced chemical transformation can be realized with
a convenient and common reaction system.
À
bears propyl and butyl groups, methylene C H oxygenation
exclusively yielded the secondary alcohol 2r, and a primary
alcohol was not detected in the crude reaction mixture. The
À
reaction of alkene 1s to give diol 2s demonstrated that C H
oxygenation may also occur on a carbon atom that is part of
a five-membered ring. Interestingly, during the reaction of
internal alkene 1t (as a ca. 70:30 mixture of geometric
isomers) with a simple alkyl chain and an amide moiety, the
second hydroxy group was predominantly introduced on the
alkyl chain to give 1,4-diol 2t. This is probably due to the
electrophilic nature of the alkoxy radical, which prefers not to
abstract a hydrogen atom from the electron-deficient a-
position of a carbonyl moiety, so that 2t’ was obtained in low
yield. In the reaction of methylenecyclooctane (1u), 1,4-diol Experimental Section
Typical procedure for the synthesis of 1,4-diols from alkenes: Iron
phthalocyanine (45.5 mg, 0.08 mmol), dimethylsulfide (10.0 mg,
0.16 mmol), and sodium borohydride (45.4 mg, 1.2 mmol) were
2u and a small amount of hemiacetal 2u’ were obtained,
À
which indicates that C H oxygenation proceeded in good
yield (overall yield: 57%). The formation of 2u’ implies that
a minor pathway exists that leads to the formation of a ketone
intermediate.[18]
added to
a solution of 2,4-dimethyl-1-pentene (1a; 78.5 mg,
0.8 mmol) in ethanol (8 mL) at room temperature; the mixture was
stirred at the same temperature for 2 h under an oxygen atmosphere
(balloon). The reaction mixture was filtered, and the solvent was
removed under reduced pressure. The resultant residue was purified
by column chromatography on silica gel (n-hexane/EtOAc, 1:1) to
give 2,4-dimethylpentane-1,4-diol (2a; 50.2 mg, 48%) as a colorless
oil. For details, see the Supporting Information.
À
C H oxygenation of the tertiary carbon atoms in alkenes
1v–y proceeded to afford 1,4-diols 2vw (from 1v and 1w), 2x,
and 2y, which bear two tertiary hydroxy groups. The some-
what lower yield of 2y may be rationalized in the same terms
as the diminished yield of the reaction with 1t. Alkene 1z,
which bears butyl and isopentyl groups, predominantly
afforded tertiary alcohol 2z, along with a small amount of
secondary alcohol 2zꢀ (tentatively identified). Generally, the
bond dissociation energies (BDEs) for the homolytic cleavage
Received: October 5, 2013
Revised: December 17, 2013
Published online: February 2, 2014
À
of C H bonds tend to decrease with an increase in the
À
Keywords: C H oxygenation · iron catalysis · oxygen ·
radical reactions · synthetic methods
.
number of substituents (primary > secondary > tertiary),[13,22]
and the results of the reactions with 1r and 1z are consistent
À
with this trend. Therefore, the rate of C H oxygenation in the
present reaction seems to be greatly influenced by the BDE,
as is the case for many known C H functionalization
[1] a) M. B. Smith, J. March, Marchꢀs Advanced Organic Chemistry,
5th ed., Wiley, New York, 2001; b) Comprehensive Organic
À
Angew. Chem. Int. Ed. 2014, 53, 2730 –2734
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
2733

.
Angewandte
Communications
Functional Group Transformations II, Vol. 2, (Eds.: A. R.
Katrinsky, R. J. K. Taylor), Elsevier, Amsterdam, 2005.
[2] For examples of anti-Markovnikov hydration, see: a) G. Dong, P.
Teo, Z. K. Wickens, R. H. Grubbs, Science 2011, 333, 1609 –
1612; b) L. Li, S. B. Herzon, J. Am. Chem. Soc. 2012, 134,
17376 – 17379.
[3] K. Takahashi, M. Yamashita, T. Ichihara, K. Nakano, K. Nozaki,
Angew. Chem. 2010, 122, 4590 – 4592; Angew. Chem. Int. Ed.
2010, 49, 4488 – 4490.
j) P. E. Gormisky, M. C. White, J. Am. Chem. Soc. 2013, 135,
14052 – 14055.
ˇ
[13] For a review on radical hydrogen shift reactions, see: a) Z.
ˇ
´
Cekovic, Tetrahedron 2003, 59, 8073 – 8090; for recent examples,
see: b) R. Kundu, Z. T. Ball, Org. Lett. 2010, 12, 2460 – 2463;
c) A.-F. Voica, A. Mendoza, W. R. Gutekunst, J. O. Fraga, P. S.
Baran, Nat. Chem. 2012, 4, 629 – 635; d) X. Zhu, Y.-F. Wang, W.
Ren, F.-L. Zhang, S. Chiba, Org. Lett. 2013, 15, 3214 – 3217;
e) E. T. Hennessy, T. A. Betley, Science 2013, 340, 591 – 595; f) T.
Taniguchi, Y. Sugiura, T. Hatta, A. Yajima, H. Ishibashi, Chem.
Commun. 2013, 49, 2198 – 2200; g) D. Hirose, T. Taniguchi,
Beilstein J. Org. Chem. 2013, 9, 1713 – 1717; see also Ref. [10c]
and references therein.
À
[4] For recent examples of other allylic C H oxidation reactions,
see: a) P. E. Gormisky, M. C. White, J. Am. Chem. Soc. 2011, 133,
12584 – 12589; b) D. Huang, H. Wang, F. Xue, Y. Shi, Org. Lett.
2011, 13, 7269 – 7274; c) I. I. Strambeanu, M. C. White, J. Am.
Chem. Soc. 2013, 135, 12032 – 12037.
[14] a) T. Okamoto, S. Oka, J. Org. Chem. 1984, 49, 1589 – 1594; b) T.
Sugimori, S.-i. Horike, S. Tsumura, M. Handa, K. Kasuga, Inorg.
Chim. Acta 1998, 283, 275 – 278; c) S. Prateeptongkum, I. Jovel,
R. Jackstell, N. Vogl, C. Weckbecker, M. Beller, Chem.
Commun. 2009, 1990 – 1992; d) T. Taniguchi, N. Goto, A.
Nishibata, H. Ishibashi, Org. Lett. 2010, 12, 112 – 115; for
additions and corrections, see: T. Taniguchi, N. Goto, A.
Nishibata, H. Ishibashi, Org. Lett. 2010, 12, 5084; e) E. K.
Leggans, T. J. Barker, K. K. Duncan, D. L. Boger, Org. Lett.
2012, 14, 1428 – 1431; f) T. J. Barker, D. L. Boger, J. Am. Chem.
Soc. 2012, 134, 13588 – 13591; g) A. Ekomiꢃ, G. Lefꢄvre, L.
Fensterbank, E. Lacꢅte, M. Malacria, C. Ollivier, A. Jutand,
Angew. Chem. 2012, 124, 7048 – 7052; Angew. Chem. Int. Ed.
2012, 51, 6942 – 6946.
[5] Modern Oxidation Methods, 2nd ed. (Ed.: J.-E. Bꢀckvall), Wiley-
VCH, Weinheim, 2010.
[6] For recent examples of new 1,2-dihydroxylation reactions of
alkenes, see: a) Y. Feng, J. England, L. Que, Jr., ACS Catal. 2011,
1, 1035 – 1042; b) M. J. Rawling, N. C. O. Tomkinson, Org.
Biomol. Chem. 2013, 11, 1434 – 1440.
[7] a) S. E. Bode, M. Wolberg, M. Mꢁller, Synthesis 2006, 557 – 588;
b) C. Oger, Y. Brinkmann, S. Bouazzaoui, T. Durand, J.-M.
Galano, Org. Lett. 2008, 10, 5087 – 5090; c) A. Robinson, V. K.
Aggarwal, Angew. Chem. 2010, 122, 6823 – 6825; Angew. Chem.
Int. Ed. 2010, 49, 6673 – 6675.
[8] For examples of new approaches to the synthesis of 1,3-diols,
see: a) K. Chen, J. M. Richter, P. S. Baran, J. Am. Chem. Soc.
2008, 130, 7247 – 7249; b) Y. Jiao, C. Cao, Z. Zhou, Org. Lett.
2011, 13, 180 – 183; c) H. Y. Cho, Z. Yu, J. P. Morken, Org. Lett.
2011, 13, 5267 – 5269; d) P. A. Evans, A. Grisin, M. J. Lawler, J.
Am. Chem. Soc. 2012, 134, 2856 – 2859.
[9] For recent examples of the synthesis of 1,4-diols, see: a) R.
Ballini, L. Barboni, G. Giarlo, J. Org. Chem. 2003, 68, 9173 –
9176; b) R. F. de La Pradilla, I. Colomer, M. UreÇa, A. Viso,
Org. Lett. 2011, 13, 2468 – 2471; c) M. Tortosa, Angew. Chem.
2011, 123, 4036 – 4039; Angew. Chem. Int. Ed. 2011, 50, 3950 –
3953; d) A. Robinson, V. K. Aggarwal, Org. Biomol. Chem.
2012, 10, 1795 – 1801.
[10] a) H. E. Burks, L. T. Kliman, J. P. Morken, J. Am. Chem. Soc.
2009, 131, 9134 – 9135; b) R. J. Ely, J. P. Morken, Org. Lett. 2010,
12, 4348 – 4351; c) P. C. Too, Y. L. Tnay, S. Chiba, Beilstein J. Org.
Chem. 2013, 9, 1217 – 1225.
[11] a) K. Godula, D. Sames, Science 2006, 312, 67 – 72; b) P. S. Baran,
Y. Ishihara, Synlett 2010, 1733 – 1745; c) P. R. Ortiz de Montel-
lano, Chem. Rev. 2010, 110, 932 – 948; d) T. Newhouse, P. S.
Baran, Angew. Chem. 2011, 123, 3422 – 3435; Angew. Chem. Int.
Ed. 2011, 50, 3362 – 3374; e) M. Zhou, R. H. Crabtree, Chem.
Soc. Rev. 2011, 40, 1875 – 1884; f) C.-M. Che, V. K.-Y. Lo, C.-Y.
Zhou, J.-S. Huang, Chem. Soc. Rev. 2011, 40, 1950 – 1975;
[15] For a review on metal phthalocyanines, see: A. B. Sorokin,
Chem. Rev. 2013, 113, 8152 – 8191.
[16] a) T. Punniyamurthy, S. Velusamy, J. Iqbal, Chem. Rev. 2005, 105,
2329 – 2364; b) J. Piera, J.-E. Bꢀckvall, Angew. Chem. 2008, 120,
3558 – 3576; Angew. Chem. Int. Ed. 2008, 47, 3506 – 3523;
c) A. N. Campbell, S. S. Stahl, Acc. Chem. Res. 2012, 45, 851 –
863.
[17] The quantity of monoalcohol F could not be accurately deter-
mined by GC analysis of the reaction mixture because the peak
of F partially overlapped with peaks of impurities that result
from the use of NaBH4. Analysis of the reaction mixture after
quenching (with water or acids) gave peaks with poor quality
(broad or tailing).
[18] See the Supporting Information for details.
[19] a) W. Nam, M. H. Lim, S.-Y. Oh, J. H. Lee, H. J. Lee, S. K. Woo,
C. Kim, W. Shin, Angew. Chem. 2000, 112, 3792 – 3795; Angew.
Chem. Int. Ed. 2000, 39, 3646 – 3649; b) W. Nam, M. H. Lim, S.-
Y. Oh, Inorg. Chem. 2000, 39, 5572 – 5575; c) W. Nam, S. W. Jin,
M. H. Lim, J. Y. Ryu, C. Kim, Inorg. Chem. 2002, 41, 3647 – 3652.
[20] The reproducibility of the present reaction was tentatively
confirmed by running some selected reactions twice; see the
Supporting Information.
g) M. C. White, Science 2012, 335, 807 – 809.
[21] [Fe(Pc)] [$26.50/1 g (Aldrich), ¥7500/25 g (TCI)] was less
expensive than [Fe(Tpp)Cl] [$69.30/500 mg (Aldrich), ¥22500/
500 mg (Wako)] in 2013. Furthermore, impurities of [Fe(Tpp)Cl]
often contaminated the product.
[22] a) J. Berkowitz, G. B. Ellison, D. Gutman, J. Phys. Chem. 1994,
98, 2744 – 2765; b) S. J. Blanksby, G. B. Ellison, Acc. Chem. Res.
2003, 36, 255 – 263.
[23] For instance, 1,8-nonanediol (7%) was isolated along with 2u
and 2u’ in the reaction of 1u. This compound was certainly
produced by a b-scission process of the alkoxy radical followed
by reduction of the resultant ketone.
[24] a) B. Meunier, S. P. de Visser, S. Shaik, Chem. Rev. 2004, 104,
3947 – 3980; b) S. Kille, F. E. Zilly, J. P. Acevedo, M. T. Reetz,
Nat. Chem. 2011, 3, 738 – 743, and references therein.
3
À
[12] For recent examples of C(sp ) H oxygenation reactions, see:
a) E. McNeill, J. Du Bois, J. Am. Chem. Soc. 2010, 132, 10202 –
10204; b) K. Kamata, K. Yonehara, Y. Nakagawa, K. Uehara, N.
Mizuno, Nat. Chem. 2010, 2, 478 – 483; c) M. A. Bigi, S. A. Reed,
M. C. White, J. Am. Chem. Soc. 2012, 134, 9721 – 9726; d) Z.
Ren, F. Mo, G. Dong, J. Am. Chem. Soc. 2012, 134, 16991 –
16994; e) E. M. Simmons, J. F. Hartwig, Nature 2012, 483, 70 –
73; f) E. McNeill, J. Du Bois, Chem. Sci. 2012, 3, 1810 – 1813;
g) S.-Y. Zhang, G. He, Y. Zhao, K. Wright, W. A. Nack, G. Chen,
J. Am. Chem. Soc. 2012, 134, 7313 – 7316; h) L. Gꢂmez, M.
Canta, D. Font, I. Prat, X. Ribas, M. Costas, J. Org. Chem. 2013,
78, 1421 – 1433; i) S. A. Moteki, A. Usui, T. Zhang, C. R.
Solorio Alvarado, K. Maruoka, Angew. Chem. 2013, 125,
8819 – 8822; Angew. Chem. Int. Ed. 2013, 52, 8657 – 8660;
2734
www.angewandte.org
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2014, 53, 2730 –2734