Stereospecific Synthesis of Alkenes by Eliminative Cross-Coupling of Enantioenriched sp3-Hybridized Carbenoids

Article abstract of DOI:10.1002/anie.201606641

1-Aryl-1,2-dialkylethenes were generated by a sequence of electrophilic substitution, 1,2-metalate rearrangement, and β-elimination initiated by the addition of enantioenriched α-(carbamoyloxy)alkylboronates to enantioenriched lithiated carbamates. The carbenoid stereochemical pairing [i.e., “like”=(S)+(S) or “unlike”=(S)+(R)] and the elimination mechanism (syn or anti), not substituent effects, determined the configuration of the trisubstituted alkene target. For example, (Z)-2,5-diphenyl-2-pentene was produced in 70 % yield with E/Z=5:95 by a like combination of Li and B carbenoids and syn (thermal) elimination whereas the E isomer was obtained in the same yield with E/Z>98:2 by an otherwise identical process involving an unlike stereochemical pairing. The concept elaborated overcomes an intrinsic limitation of traditional strategies for direct connective alkene synthesis, which cannot realize meaningful stereochemical bias unless the alkene substituents are strongly differentiated.

Full text of DOI:10.1002/anie.201606641

Angewandte
Communications
Chemie
International Edition: DOI: 10.1002/anie.201606641
German Edition: DOI: 10.1002/ange.201606641
Alkene Synthesis
Stereospecific Synthesis of Alkenes by Eliminative Cross-Coupling of
Enantioenriched sp3-Hybridized Carbenoids
Zhenhua Wu, Xun Sun, Kristin Potter, Yang Cao, Lev N. Zakharov, and Paul R. Blakemore*
Abstract: 1-Aryl-1,2-dialkylethenes were generated by
a sequence of electrophilic substitution, 1,2-metalate rearrange-
ment, and b-elimination initiated by the addition of enantioen-
riched a-(carbamoyloxy)alkylboronates to enantioenriched
lithiated carbamates. The carbenoid stereochemical pairing
[i.e., “like” = (S)+(S) or “unlike” = (S)+(R)] and the elimi-
nation mechanism (syn or anti), not substituent effects,
determined the configuration of the trisubstituted alkene
target. For example, (Z)-2,5-diphenyl-2-pentene was produced
in 70% yield with E/Z = 5:95 by a like combination of Li and
B carbenoids and syn (thermal) elimination whereas the
E isomer was obtained in the same yield with E/Z > 98:2 by
an otherwise identical process involving an unlike stereochem-
ical pairing. The concept elaborated overcomes an intrinsic
limitation of traditional strategies for direct connective alkene
synthesis, which cannot realize meaningful stereochemical bias
unless the alkene substituents are strongly differentiated.
(Scheme 1).[6] No biasing features are required within the
substituents (R1–R4) to achieve fully controlled alkene
formation with this concept. The process is trivially regiospe-
cific, and stereochemical information encoded within the two
carbenoid subunits is translated via a sequence of three
stereospecific processes [electrophilic substitution (1 + 2!3),
1,2-metalate rearrangement (3!4), and b-elimination (4!
5)] into any desired configuration of the target alkene 5.
Herein, the realization of this eliminative cross-coupling
approach for the synthesis of a series of trisubstituted alkenes
belonging to the styrene class is reported.[7]
T
he carbon–carbon double bond is of fundamental impor-
tance, and molecules containing some type of pCC system are
widespread and have broad utility. In general, carbon–carbon
double bonds are stereogenic and/or decorated non-sym-
metrically, and so synthetic methods designed to access them
should be capable of both stereo- and regiocontrol.[1] In spite
of this fact, conventional direct methods for the preparation
of alkenes, the most common class of compounds containing
pCC bonds, do not wholly address selectivity issues. For
example, carbonyl olefination based approaches are regio-
specific but good stereocontrol is dependent on the alkene
substituents being adequately differentiated by steric or
electronic factors.[2] As a consequence, excellent stereoselec-
tivity is only guaranteed for 1,2-disubstituted alkene targets,
and the stereocontrolled synthesis of tri- and tetrasubstituted
examples remains a challenge.[3] When alkenes are prepared
by alkyne elementometalation,[4] stereospecificity is achieved
but regiocontrol is dependent on the substituents being again
distinguished in some special way, and poor selectivity is
anticipated for generic internal alkynes.[5] To overcome the
limitations of existing strategies, a connective synthesis of
alkenes was envisioned by eliminative cross-coupling of
Scheme 1. Eliminative cross-coupling of enantioenriched carbenoids
for the synthesis of alkenes.
The formation of symmetric alkenes by eliminative
“dimerization” (i.e., homocoupling) of more reactive carbe-
noids is an often observed side reaction.[8] Hodgson and co-
workers deliberately exploited this phenomenon to make
2-buten-1,4-diol derivatives by homocoupling of 1-lithiooxir-
anes and demonstrated that the E/Z ratio of the olefin
product was dependent on the enantiopurity of the carbenoid,
as anticipated.[9] The synthesis of non-symmetric alkenes by
cross-coupling of racemic carbenoids has been occasionally
explored; however, these approaches offer poor, or else not
generalizable, stereoselectivity.[10] In a seminal effort that goes
a long way to validate the premise of the above scheme,
Matteson and co-workers described the cross-coupling of
enantioenriched a-chloroalkylboronates and enantioenriched
Stille-type carbanions to afford stereodefined contiguous
stereodiad motifs bearing vicinal boron and oxygen substitu-
ents [Eq. (1); MOM = methoxymethyl].[11] Elimination was
not pursued; however, treatment of the b-oxyboronate
enantioenriched sp3-hybridized carbenoids
1
and
2
[*] Z. Wu, X. Sun, K. Potter, Y. Cao, Dr. L. N. Zakharov,
Prof. Dr. P. R. Blakemore
Department of Chemistry, Oregon State University
Corvallis, OR 97331 (USA)
E-mail: paul.blakemore@oregonstate.edu
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under:
http://dx.doi.org/10.1002/anie.201606641.
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1
These are not the final page numbers!

Angewandte
Communications
Chemie
products with a basic nucleophile would be expected to
induce anti b-elimination to yield alkenes.
anti elimination, a like stereochemical pairing of scalemic
samples of 9 and 10p was selected to target (E)-11 (entry 3).
In the event, it was discovered that addition of (S)-10p (97%
ee) to (S)-9 (97% ee) at ꢀ788C followed by warming to room
temperature gave pre-elimination adduct lk-13p (via ate
complex lk-12p) as an essentially single regio-/diastereoiso-
mer [Eq. (2)].[18]
The first two steps of eliminative cross-coupling (1 + 2!
3!4) resemble stereospecific reagent-controlled homologa-
tion (StReCH),[12] a process typically used for the iterative
chain extension of boronic esters by sequential insertions of
[13]
ꢀ
scalemic carbenoids into the C B bond.
Studies by
Aggarwal et al. have established that Hoppe-type lithiated
carbamates are a robust class of carbenoids for StReCH.[14]
Significantly, they demonstrated that fully substituted orga-
nolithium reagents derived from enantiopure secondary
O-benzylic carbamates are capable of stereospecific insertion
into boronic esters.[15] Given this precedent and wishing to
eschew the targeting of easily made 1,2-disubstituted alkenes,
we focused our experiments on the synthesis of 1-aryl-1,2-
dialkylethenes, a class of styrenes that are difficult to prepare
stereoselectively by traditional direct means.[16] To establish
the basic parameters for this styrene synthesis, eliminative
cross-coupling of lithiated carbamate 9 with a-carbamoyloxy-
boronates 10p and 10n to generate 11 was examined
(Table 1).[17]
Treatment of lk-13p with NaOMe induced anti elimination to
give (E)-11 in good overall yield and with a level of
stereoselectivity commensurate with statistical considera-
tions.[19] To conclude this proof-of-concept study, the unlike
stereochemical pairing of 9 and 10p was studied next under
essentially identical conditions (entry 4). The thermodynami-
cally less stable alkene isomer (Z)-11 was obtained in
comparable yield and with stereoselectivity only slightly
lower than that previously observed.
In an effort to improve the yield, a neopentylglycol
boronate (10n)[20] was examined as a sterically less encum-
bered alternative to the pinacol boronic ester used above
(10p). The like stereochemical pairing of 9 and 10n proved
satisfactory to access (E)-11 (entry 5), but the unlike combi-
nation anticipated to target (Z)-11 instead gave a mixture of
alkene isomers favoring (E)-11 (entry 6). Upon closer scru-
tiny, spectroscopic analysis of the reaction mixture
revealed that a significant quantity of (E)-11 was
present before the alkoxide addition stage. In this
case, spontaneous syn elimination of the pre-elimi-
nation adduct ul-13n by a bora-Wittig mecha-
nism[2,21] competed with the usual alkoxide-mediated
anti elimination pathway [Eq. (3)].[22] The fact that
neopentylglycol boronates allow for syn elimination
After optimizing reaction variables for an alkene syn-
thesis involving an elimination stage triggered by exogenous
Table 1: A model eliminative cross-coupling reaction.
was deliberately exploited by simply omitting alk-
oxide addition and heating the reaction mixture
(toluene, 808C) following ate complex rearrange-
ment (method B). In this manner, (Z)-11 was now
successfully obtained from (S)-10n by pairing it in
a like fashion with (S)-9 (entry 7). (E)-11 was
similarly targeted from (S)-10n by unlike stereo-
chemical pairing with (R)-9 (entry 8). Thermolytic
syn elimination from pinacol boronate pre-elimina-
tion adducts lk-13p and ul-13p was too sluggish at
808C to be practically useful.
Entry Li carb. B carb.
Pairing
Method Target
Yield [%] E/Z
1
2
3
4
5
6
7
8
(ꢁ)-9
(ꢁ)-9
(S)-9
(R)-9
(S)-9
(R)-9
(S)-9
(R)-9
(ꢁ)-10p intrinsic
A[b]
(E+Z)-11 80
54:46
(S)-10p like/unlike A[b]
(E+Z)-11 70
56:44
98:2
(S)-10p like
(S)-10p unlike
(S)-10n like
(S)-10n unlike
(S)-10n like
(S)-10n unlike
A[b]
A[b]
A
A
B
(E)-11
(Z)-11
(E)-11
(Z)-11
(Z)-11
(E)-11
69
72
69
65
70
70
6:94
>98:2
52:48
5:95
B
>98:2
[a] Generated by lithiation using s-BuLi or t-BuLi, Et2O, ꢀ788C, 20 min. [b] Reaction
conducted in Et2O solvent only. Bneo=B[OCH2(CMe2)CH2O], Bpin=
B[O(CMe2)2O], CbO=i-Pr2NCO2.
At this juncture, two viable eliminative cross-
coupling methods for the stereospecific synthesis of
styrene 11 had been identified, and we sought to
alkoxide anion (method A), it was observed that coupling of
(ꢁ)-9 and (ꢁ)-10p showed little stereoselectivity (Table 1,
entry 1). This is an ideal result because it reveals that like
(“homochiral”) and unlike (“heterochiral”) stereochemical
pairings of 9 and 10p occur at similar rates. Eliminative cross-
coupling using (ꢁ)-9 and (S)-10p gave styrene 11 with E/Z
ꢂ 1:1 as expected (entry 2). Assuming that method A involves
determine the limit of these approaches for the preparation of
other
1-aryl-1,2-dialkylethenes (Table 2). All alkenes were sepa-
rately targeted in both E and Z configurations, and for each
isomer, outcome data for the coupling method that gave the
best result among those evaluated are illustrated. In general,
the E isomers were best accessed by like pairings and anti
2
www.angewandte.org
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
These are not the final page numbers!

Angewandte
Communications
Chemie
even in those cases where the olefin was exocyclic to
a benzofused bicyclic scaffold (20, 21, and 22).[23]
Anomalous behavior observed during attempts to secure
a-vinyl naphthalene 17 necessitated the development of
a new method (C) to achieve stereoselectivity. Uniquely in
this case, and possibly owing to heightened steric hindrance
caused by the a-naphthyl substituent, O atom migration
competed with the canonical mechanism for 1,2-metalate
rearrangement, and stereocontrol was forfeit. Addition of
MgBr2·OEt2 after ate complex formation facilitated clean
formation of the borinate product of O atom migration (25),
which was transformed stereospecifically into the olefin,
presumably via boronate 26, upon heating [Eq. (4)]. Double
inversion of stereochemistry at the benzylic carbon atom
originating from the lithiated carbamate accounts for the
generation of the E alkene from a like carbenoid pairing and
a syn elimination pathway (and similarly, a Z alkene from an
unlike pairing).
elimination (method A) using neopentylglycol (neo) or
pinacol (pin) boronates whereas like pairings and syn
elimination (method B) as applied to neopentylglycol boro-
nates were typically superior for the synthesis of Z isomers.
When syn elimination was desired, it was found that an
aqueous work-up to remove basic species (which may trigger
anti elimination) prior to thermolysis led to improved
stereoselectivity. An acceptable level of stereocontrol was
possible for a majority of alkene targets, and in all cases, it was
possible to selectively synthesize the E or the Z isomer. The
coupling efficiency diminished as the steric demand of the
substituents surrounding the double bond increased (11, 18,
19, and 23) but it was impressive that highly strained
Z alkenes could be targeted successfully (e.g., 17 and 23),
Table 2: Synthesis of E- and Z-configured 1-aryl-1,2-dialkylethenes by
eliminative cross-coupling.[a]
Finally, in a foray to gauge the potential of eliminative
carbenoid cross-coupling for the synthesis of more complex
alkenes, conversion of (+)-a-pinene-derived boronate (10S)-
27[24] into the precursor of a known chiral pentadienyl anionic
ligand [conjugated diene (E)-28][25] was explored (Scheme 2).
Separate transformations targeting both the E and Z isomers
of diene 28 proceeded in good yield, and it was notable that
syn elimination was achievable from a pinacol boronate,
presumably because of the doubly activated (allylic/benzylic)
Scheme 2. Stereoselective synthesis of a conjugated diene from an
(+)-a-pinene-derived boronate.
nature of the relevant pre-elimination adducts in this case.
Synthesis of (E)-28 benefitted from the addition of trime-
thylborate as a nucleophile scavenger after ate complex
formation [without B(OMe)3: 39% yield, E/Z = 97:3]; how-
ever, the presence of this additive was detrimental when (Z)-
28 was targeted [with B(OMe)3: 49% yield, E/Z = 35:65].
In summary, we have demonstrated that eliminative cross-
coupling of enantioenriched carbenoids is a viable strategy for
[a] Optimal method for targeting the E (top) or Z (bottom) isomer
indicated by: boronate type (pin or neo)·stereochemical pairing (like or
unlike)·method (see Table 1 for methods A and B; method C: Et2O/
toluene, ꢀ788C, 1 h; then MgBr2·OEt2, ꢀ788C to RT, 16 h, workup; then
toluene, 808C, 16 h). [b] Data for 11 recapitulated from Table 1 (entries 5
and 7). In a majority of examples, the enantiopurity of the carbenoid
components was ꢃ96% ee. See the Supporting Information for specific
details of individual reactions.
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
3
These are not the final page numbers!

Angewandte
Communications
Chemie
StReCH, the stereoinductive substrate-controlled Matteson
homologation, see: c) D. S. Matteson, J. Org. Chem. 2013, 78,
10009 – 10023.
the stereospecific assembly of alkenes. The double bond
configuration is programmed by carbenoid stereochemical
pairing (like or unlike) and the type of elimination (syn or
anti). Thus, by contrast to traditional methods for alkene
synthesis that rely on substituent effects for stereocontrol, the
advocated approach is in principle applicable to the stereo-
selective synthesis of essentially any type of stereogenic
alkene, no matter how subtle, or otherwise, the features
distinguishing the stereoisomers. Herein, the concept was
established for trisubstituted alkenes of the styrene class, and
it remains to be extended to other important types of olefins,
including tetrasubstituted derivatives. Studies along these
lines, and conceptually related work directed at the synthesis
of allenes and higher cumulenes, are ongoing and will be the
subject of future reports.
[13] For representative examples, see: a) X. Sun, P. R. Blakemore,
Org. Lett. 2013, 15, 4500 – 4503; b) M. Burns, S. Essafi, J. R.
Bame, S. P. Bull, M. P. Webster, S. Balieu, J. W. Dale, C. P. Butts,
J. N. Harvey, V. K. Aggarwal, Nature 2014, 513, 183 – 188.
[14] D. Leonori, V. K. Aggarwal, Acc. Chem. Res. 2014, 47, 3174 –
3183.
[15] a) J. L. Stymiest, V. Bagutski, R. M. French, V. K. Aggarwal,
Nature 2008, 456, 778 – 783; b) T. G. Elford, S. Nave, R. P.
Sonawane, V. K. Aggarwal, J. Am. Chem. Soc. 2011, 133, 16798 –
16801; c) C. G. Watson, A. Balanta, T. G. Elford, S. Essafi, J. N.
Harvey, V. K. Aggarwal, J. Am. Chem. Soc. 2014, 136, 17370 –
17373.
[16] For representative examples, see: a) T. Okazoe, K. Takai, K.
Utimoto, J. Am. Chem. Soc. 1987, 109, 951 – 953; b) S. F. Martin,
D. Daniel, R. J. Cherney, S. Liras, J. Org. Chem. 1992, 57, 2523 –
2525; c) E. Vedejs, J. Cabaj, M. J. Peterson, J. Org. Chem. 1993,
58, 6509 – 6512; d) Q. Sha, Y. Ling, W. Wang, Y. Wei, Adv. Synth.
Catal. 2013, 355, 2145 – 2150.
Acknowledgements
[17] Lithiated carbamates were generated essentially as previously
described by Aggarwal et al. (Ref. [15a]), beginning with cata-
lytic enantioselective reduction of prochiral ketones using
Noyori transfer hydrogenation. a-Carbamoyloxy boronates
were made by (ꢀ)-sparteine/s-BuLi mediated lithiation – bory-
lation of the appropriate O-alkyl N,N-diisopropyl carbamates
according to the method of Hoppe et al.; see: E. Beckmann, V.
Desai, D. Hoppe, Synlett 2004, 2275 – 2280.
Oregon State University is thanked for a General Research
Fund (GRF) award to support this research.
Keywords: alkenes · carbenoids · metalate rearrangements ·
organometallic reagents · stereoablation
[18] In this case, the putative ate complex lk-12p rearranged with
selective loss of the benzylic OCb nucleofuge; however, it should
be noted that such regioselectivity is not generally required for
successful eliminative cross-coupling because both possible
regioisomers would converge to the same alkene. The relative
stereochemistry of lk-13n produced in an analogous manner was
proven by oxidative deborylation (NaOOH) followed by
cyclization (NaH, DMF, 1008C) to give the corresponding
epoxide, which was analyzed by 1H NMR spectroscopy
(NOESY). See the Supporting Information for details.
[19] Given that both carbenoids in this case had 66:1 e.r. (97% ee)
the anticipated stereoselectivity for alkene formation would be
E/Z = (662 + 1)/(66 + 66) ꢂ 33:1 (i.e., 97:3). See Scheme 1 for the
general formula.
[20] X-ray diffraction analysis of (S)-10n confirmed its gross
structure and absolute stereochemistry. This a-carbamoyloxy
boronate was observed to exist (in the solid state) in cyclic form
with the carbonyl group O atom coordinated to a quaternized
B atom. CCDC 1491635 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre.
[21] a) M. W. Rathke, R. Kow, J. Am. Chem. Soc. 1972, 94, 6854 –
6856; b) D. S. Matteson, R. J. Moody, P. K. Jesthi, J. Am. Chem.
Soc. 1975, 97, 5608 – 5609; c) A. Pelter, D. Buss, E. Colclough, B.
Singaram, Tetrahedron 1993, 49, 7077 – 7103; d) T. Tomioka, Y.
Takahashi, T. G. Vaughan, T. Yanase, Org. Lett. 2010, 12, 2171 –
2173; e) J. R. Coombs, L. Zhang, J. P. Morken, Org. Lett. 2015,
17, 1708 – 1711.
[1] The Chemistry of Alkenes in The Chemistry of the Functional
Groups (Ed.: S. Patai), Wiley, New York, 1964.
[2] “Olefination of Carbonyl Compounds by Main-Group Element
Mediators”: P. R. Blakemore in Comprehensive Organic Syn-
thesis, 2nd ed., Vol. 1 (Eds.: G. A. Molander, P. Knochel),
Elsevier, Oxford, 2014, pp. 516 – 608.
[3] a) E.-i. Negishi, Z. Huang, G. Wang, S. Mohan, C. Wang, H.
Hattori, Acc. Chem. Res. 2008, 41, 1474 – 1485; b) A. B. Flynn,
W. W. Ogilvie, Chem. Rev. 2007, 107, 4698 – 4745.
[4] a) E.-i. Negishi, G. Wang, H. Rao, Z. Xu, J. Org. Chem. 2010, 75,
3151 – 3182; b) B. M. Trost, Z. T. Ball, Synthesis 2005, 853 – 887.
[5] For representative examples, see: a) H. Yoshida, I. Kageyuki, K.
Takaki, Org. Lett. 2013, 15, 952 – 955; b) Y. Li, X. Liu, H. Jiang,
Z. Feng, Angew. Chem. Int. Ed. 2010, 49, 3338 – 3341; Angew.
Chem. 2010, 122, 3410 – 3413; c) A. Yada, T. Yukawa, Y. Nakao,
T. Hiyama, Chem. Commun. 2009, 3931 – 3933.
[6] Herein, “carbenoid” refers to any species containing a C atom
bonded to both an electrofugal (M) and a nucleofugal (X) atom/
group.
[7] Presented in part at the 251st ACS National Meeting, San Diego,
CA, March 13 – 17, 2016; Z. Wu, P. R. Blakemore, American
Chemical Society, Washington, DC, 2016, paper ORGN 110.
[8] a) G. Kçbrich, Angew. Chem. Int. Ed. Engl. 1967, 6, 41 – 52;
Angew. Chem. 1967, 79, 15 – 27; b) C. R. Emerson, L. N.
Zakharov, P. R. Blakemore, Chem. Eur. J. 2013, 19, 16342 –
16356.
[22] syn Elimination from ul-13n is more rapid than from its epimer
lk-13n because for the latter, the two largest substituents (Ph
and BnCH2) eclipse one another in the necessary reactive
conformation. Facile spontaneous syn elimination from adducts
such as ul-13n (leading to E alkenes) means that Z alkenes
should not be targeted from neopentylglycol boronates using
unlike pairings and anti elimination.
[9] D. M. Hodgson, C. D. Bray, N. D. Kindon, Org. Lett. 2005, 7,
2305 – 2308.
[10] a) T. Satoh, A. Kondo, J. Musashi, Tetrahedron 2004, 60, 5453 –
5460; b) A. Abramovitch, I. Marek, Eur. J. Org. Chem. 2008,
4924 – 4931.
[11] D. S. Matteson, P. B. Tripathy, A. Sarkar, K. M. Sadhu, J. Am.
Chem. Soc. 1989, 111, 4399 – 4402.
[23] Eliminative dimerization of the lithiated carbamate was not
a significant side reaction except for the a-lithioindanyl carba-
mate leading to alkene 20 (see the Supporting Information). The
[12] a) P. R. Blakemore, S. P. Marsden, H. D. Vater, Org. Lett. 2006,
8, 773 – 776; b) P. R. Blakemore, M. S. Burge, J. Am. Chem. Soc.
2007, 129, 3068 – 3069; for a discourse on the antecedent of
4
www.angewandte.org
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
These are not the final page numbers!

Angewandte
Communications
Chemie
root cause of low yields is as yet unclear, and we speculate that
occurrences of poor stereoselectivity are due to competition
between syn and anti elimination pathways.
[25] A. C. Fecker, B.-F. Craciun, M. Freytag, P. G. Jones, M. C.
Walter, Organometallics 2014, 33, 3792 – 3803.
[24] T. Hꢀmery, J. Becker, R. Frçhlich, D. Hoppe, Eur. J. Org. Chem.
2010, 3711 – 3720.
Received: July 8, 2016
Published online: && &&, &&&&
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
5
These are not the final page numbers!

Angewandte
Communications
Chemie
Communications
Alkene Synthesis
3D to 2D: Stereochemical information
encoded in a pair of scalemic carbenoid
reagents controls the geometry of the
alkene products formed by their elimina-
tive cross-coupling. The configuration of
the alkene is determined by the carbenoid
stereochemical pairing (like or unlike) and
the elimination mechanism (syn or anti),
but not by the nature of the substituents.
Z. Wu, X. Sun, K. Potter, Y. Cao,
L. N. Zakharov,
P. R. Blakemore*
&&&& — &&&&
Stereospecific Synthesis of Alkenes by
Eliminative Cross-Coupling of
Enantioenriched sp3-Hybridized
Carbenoids
6
www.angewandte.org
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
These are not the final page numbers!