; Gold, B.

The Effect of a Hydroxy Protecting Group on the PtCl2-Catalyzed Cyclization of Dienynes—A Novel, Efficient, and Selective Synthesis of Carbocycles.

derivatives with water under external-oxidant-free conditions. Zn(OTf)2. González-Rodríguez, C.; Escalante, L.; Varela, J.A. 18, 108-111. ; Khan, S.I. Balog, A.; Geib, S.J. ; Nenajdenko, V.G. ; Chen, A.C.; Calhoun, L.A. A Demonstration of the Primary Stereoelectronic Effect in the Baeyer–Villiger Oxidation of α-Fluorocyclohexanones.

Y. Zhou, Z. Li, X. Yang, X. Chen, M. Li, T. Chen, S.-F. Yin, Cyclic ketones.

protonation and Suzuki cross-coupling of the vinyl boronate. Scott, L.T.

highly efficient directing groups. The high energy packed in alkyne functional group makes alkyne reactions highly thermodynamically favorable and generally irreversible. D. Xing, B. Guan, G. Cai, Z. Fang, L. Yang, Z. Shi, Org. Am. It is important to note that in order to keep the overall reaction as a “redox neutral” process, the final fate of the two alkyne carbons has to be opposite. Mukherjee, A.; Pati, K.; Liu, R.-S. A Convenient Synthesis of Tetrabenzo-[de,hi,mn,qr]naphthacene from Readily Available 1,2-Di(phenanthren4-yl)ethyne. catalytic amount of aniline, 3-hydroxyketones can be obtained in high yield

Ligand Effects in Homogeneous Au Catalysis.

unique role of silicon in this system.

B. C. Chary, S. Kim, J. Org.

While one of the carbons ends as part a methyl group (reduced relative to alkyne), the other one ends up as C1 of a dihydroimidazole (oxidized relative to alkyne; The subsequent intramolecular Michael addition step is sensitive to the nature of the amine. Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, USA, Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Science, 630090 Novosibirsk, Russia, Novosibirsk State University, 2, Pirogova Str., 630090 Novosibirsk, Russia. The ozonolysis of 1,2‐dimethyl propene produces both 2‐propanone (a ketone) and ethanal (an aldehyde). ; Rhee, Y.H. Thus, “classic carbonyl chemistry” can be accessed through alkynes, and new transformations can be engineered by unmasking the hidden carbonyl nature of alkynes. The fragmentation proceeds most effectively in refluxing pyridine with the 50-fold excess of the nucleophile (, More important is the possibility of expanding the alkyne fragmentation reactions to compounds with other functional groups, also positioned away from the alkyne moiety by the example of family of nitro-substituted diaryl alkynes with different positions of the acceptor NO, This chemistry can be expanded to alkynes with electron-deficient heterocycle substituents such as the pyridine moiety (. ; Albrecht-Schmitt, T.E. Teles, J.H. ; Toste, F.D.

García, H.; Iborra, S.; Primo, J.; Miranda, M.A. Part 21. The p electrons act pairs as a Lewis base. Soc., 2002, 124, 3824-3825. conversion of alkynes to their corresponding vinyl triflates. Furthermore, the presence of two orthogonal π-bonds that can be manipulated separately enables flexible synthetic cascades stemming from alkynes.

For anionic nucleophiles, exo-cyclizations are preferred in the absence of large thermodynamic or electronic bias [, For the intramolecular attack of negatively charged nucleophiles at alkynes, the general stereoelectronic factors favor exo cyclizations [, In this section, we will illustrate some of the features for alkyne cyclizations, mostly using, Base-catalyzed cyclizations of aliphatic alcohols exclusively follow the 5-exo-path where the cyclic vinyl anion is trapped by protonation, thus activating another acyclic alcohol. ; Miguel, A.A. Hyperconjugation. Reference Reviews and Accounts ARKIVOC 2013 (i) 396-417 Page 397 © ARKAT-USA, Inc. 1. A subsequent reduction gives

HTIB mediates an oxidative transposition of vinyl halides to provide α-halo Chem. from both alkyl- and aryl-substituted haloalkynes and wide functional group Of course, chemical inertness can be both a blessing and a curse but, in the case of alkynes, a breakthrough that greatly facilitated their application in chemical synthesis came with the development of alkyne-selective (“alkynophilic”) π-acidic metal catalysts [, Comparison of alkynes and carbonyls as starting materials for the synthesis of enol ethers and ketals is given in, In the presence of suitable π-acidic catalysts, the vinyl ethers obtained from alkynes can also be further converted into ketals. Hashmi, A.S.K. The ozonolysis of an alkene. Goodwin, J.A. Author to whom correspondence should be addressed.
Rules for ring closure. Eglinton, G.; Jones, E.R.H.

terminal and internal alkynes is based on TiCl4-catalyzed
Chem. 2006, 128, 74-75.

Hassall, C.H.

; Krische, M.J. Alkynes as Synthetic Equivalents to Stabilized Wittig Reagents:  Intra- and Intermolecular Carbonyl Olefinations Catalyzed by Ag(I), BF3, and HBF4. Because the carbonyl group is highly polar, aldehydes and ketones are “pre-activated” for reaction with nucleophiles and their selectivity is “pre-programmed”. allylation reactions with primary imines provide vinyl boronates which may Ketones containing alkene and alkyne units are often called unsaturated ketones. Hydration of Alkyne . Subscribe to receive issue release notifications and newsletters from MDPI journals, You can make submissions to other journals. ; Bityukov, O.V. tridentate phosphine ligand, and zinc exhibits a higher reactivity than the ; Kurilenko, V.M. ; Lin, J.B.; Brosmer, J.L. are grateful to the National Science Foundation (CHE-1800329) for support of this research. ketones as useful and polyvalent synthetic precursors. Dudnik, A.; Chernyak, N.; Gevorgyan, V. Copper-, Silver-, and Gold Catalyzed Migratory Cycloisomerization Leading to Heterocyclic Five-Membered Rings. Byers, P.M.; Rashid, J.I. B. R. Travis, R. S. Narayan, B. Borhan, J. ; Baranov, D.S. However, at higher temperatures this intermediate undergoes a stereoelectronically favorable [. ; Li, H.; Lohse, A.G.; Hayashi, R.; Lu, Z.; Zhang, Y.; Hsung, R.P. Sze, E.M.L.

Although intramolecular ketalization of carbonyls is more favorable thermodynamically than its intermolecular version (, Both inter- and intramolecular alkoxylations of alkynes have been reported using various alkynophilic metal salts. Vasilevsky, S.F.