Propyne synthesis

Suggest an efficient synthesis of trans 2 heptene from propyne... 

Assume that you need to prepare 4 methyl 2 pentyne and discover that the only alkynes on hand are acetylene and propyne You also have available methyl iodide isopropyl bromide and 1 1 dichloro 3 methylbutane Which of these compounds would you choose in order to perform your synthesis and how would you carry it out" ... 

After the initial claim of the synthesis of an oxirene (by the oxidation of propyne Section 5.05.6.3.1) this system reappeared with the claim 31LA(490)20l) that 2-chloro-l,2-diphenyl-ethanone (110) reacted with sodium methoxide to give diphenyloxirene (111), but it was later shown (52JA2082) that the product was the prosaic methoxy ketone (112 Scheme 97) (the formation of 111 from 110 would be an a-elimination carbene-type reaction). Even with strong, nonnucleophilic bases, (110) failed to provide evidence of diphenyloxirene formation (64JA4866). 

H-pyran synthesis from, 3, 759 Propyne, 3-(2-amino-1 -benzimidazolyl)-isomerization, 5, 450 Propynoic acid, phenyl-ethyl ester... 

Suggest an efficient synthesis of fram-2-heptene from propyne ] and any necessary organic or inorganic reagents. I... 

The fact that pentacarbonyl carbene complexes react with enynes in a chemo-selective and regiospecific way at the alkyne functionality was successfully applied in the total synthesis of vitamins of the Kj and K2 series [58]. Oxidation of the intermediate tricarbonyl(dihydrovitamin K) chromium complexes with silver oxide afforded the desired naphthoquinone-based vitamin K compounds 65. Compared to customary strategies, the benzannulation reaction proved to be superior as it avoids conditions favouring (E)/(Z)-isomerisation within the allylic side chain. The basic representative vitamin K3 (menadione) 66 was synthesised in a straightforward manner from pentacarbonyl carbene complex 1 and propyne (Scheme 38). 

The second example involves the synthesis of ortho-dipropynylated arenes (Scheme 4.12b), which serve as precursors to tribenzocyclyne by way of an alkyne metathesis reaction (see also Scheme 6.31). Here, a Sonogashira reaction was carried out in a pre-pressurized (propyne at ca. 2.5 bar) sealed microwave vessel in a standard single-mode microwave reactor. Double-Sonogashira coupling of the dibromodiiodo-benzene was completed within 20 min at 110 °C [30]. 

Trofimov has extended his previously reported heterocyclization of ketoximes 39 with acetylene to propyne or its isomer allene in superbase systems (MOR/DMSO M = K, Cs, R = H, t-Bu) to afford a facile synthesis of substituted pyrroles 40 and 41 . Due to a fast propyne to allene protropic isomerization under the reaction conditions, the product is the same regardless of which species is employed. 

The reaction leading to 20 was used to prepare 25 (Scheme 3.2-13) [35], starting from diethyl(propyn-l-yl)borane which served as a versatile reagent for the synthesis of other carboranes (vide infra). l,l-Bis(diethyl-boryl)propene 23 can be detected and isolated, whereas it was not possible to identify l,l,l-tris(diethylboryl)propane 24 in the reaction mixture. 

Regardless of whether the Pd-catalyzed coupling or alkyne metathesis is utilized to make PAEs, the critical step is the synthesis of the diiodoarene monomers. In this section some of the more interesting syntheses are showcased. The synthesis of dipropynyldi-tert-butylnaphthalene is shown in Scheme 5. Starting from naphthalene, Friedel-Crafts alkylation with 2-chloro-2-methylbutane gives a mixture of two di-tert-butylnaphthalenes that are separated by crystallization. Iodination of the correct isomer is followed by a Pd-catalyzed coupling of propyne to the diiodide to give the desired l,5-dipropynyl-3,8-di-tert-butyl-naphthalene [56] ready for ADIMET. 

Scheme 1 Synthesis of the allenylidene complex 1 from l,l-diphenyl-2-propyn-l-ol...

Although a two-step synthesis of l,l -(l,3-phenylene)bis-(3-phenyl-2-propyn-l-one) (1,3-PPPO) has been reported [8], we found that 1,3-PPPO could also be prepared from a one-step route, starting from iso-phthaloyl chloride and phenylacetylene, employ-... 

Benzofuranyl)pyrroles, 2-(2-thienyl)pyrroles , 2,2 -dipyrroles, 3-(2-pyr-rolyl)indoles , 2-(2-benzimidazolyl)pyrroles and2-(2-, 3- and4-pyridyl)pyrroles were prepared using this method. Reaction of alkynes (for example, propyne) or allene with ketoximes in a superbase system (MOH/DMSO) leads to 2,5-di- or 2,3,5-trisubstituted pyrroles Pyrroles and dipyrroles were synthesized also from corresponding dioximes and acetylene in a KOH/DMSO system It has also been shown that 1,2-dichloroeth-ane can serve as a source of acetylene in pyrrole synthesis. Oxime 52 in the system acetylene/RbOH/DMSO at 70 °C afforded a mixture of three pyrroles 53-55 in low yields (equation 23). The formation of product 53 occurred through recyclization of pyrrolopy-ridine intermediate. ... 

Bowman et al. reported the total synthesis of ellipticine (228) involving an imidoyl radical cascade reaction (730). For this key step, the required imidoyl radical was generated from the imidoyl selanide 1290, which was obtained from ethyl 2-(4-pyridyl)acetate (1286). Reaction of 1286 with LDA, followed by addition of methyl iodide, led to the corresponding methyl derivative 1287. Treatment of 1287 with 2-iodoaniline (743) in the presence of trimethylaluminum (AlMes) afforded the amide 1288. Using Sonogashira conditions, propyne is coupled with the amide 1288 to afford the aryl acetylene 1289. The aryl acetylene 1289 was transformed to the... 

The compound shown below is a constitutent of the pheromone of the codling moth. It has been synthesized using n-propyl bromide, propyne, 1-pentyne, ethylene oxide, and C02 as the source of the carbon atoms. Devise a route for such a synthesis. Hint Extensive use of the chemistry of organocopper reagents is the basis for the existing synthesis. 

Copper(I) acetylide is used in a diagnostic test for CH unit to prepare pure copper powder in purification of acetylene and as a catalyst in the synthesis of acrylonitrile and 2-propyn-l-ol. 

Pyrazine 168 underwent cross-coupling with propyne in the tri-o-tolylphosphine, and copper(l) iodide to provide 170. The isocyanate or methyl chloroformate and sodium hydride to give An isolated example of the synthesis of chiral pteridines from a (Scheme 33). 2-Isothiocyanatopyrazine-3-carboxylates have been isothiocyanatopyrazine-2-carboxylate 172 reacted with R)- —) provided the pteridine derivative 173 and uncyclized pyrazine with pyridine precursors afforded pyrido[2,3 Pytitnidines. 

One of the most versatile methodologies of EPC synthesis of allenes is the chirality transfer reaction which involves highly stereoselective, mechanism-controlled, metal-mediated propyn-yl-allenyl transpositions. Of these, the organocopper(l)-mediated reactions are especially useful and provide a relatively straightforward route to a broad variety of allenes of high enantiomeric purity. 

Problem 8.9 Outline a synthesis of propyne from isopropyl or propyl bromide. 

Acetylenic compounds may in some cases be suitable sources of 1,3-dioxo precursors as shown for propynal in the synthesis of 85a-d.62,l27 131 Similarly, the preparation of probable 4//-pyran derivative 91 (61.7%) may be explained by a hydration catalyzed with Zn2+ ions, which leads to a 1,5-dicarbonyl intermediate.138... 

K. Nagai, T. Masuda, T. Nakagawa, B.D. Freeman, and I. Pinnau, Poly[l-(trimethylsilyl)-l-propyne] and related polymers Synthesis, properties and functions, Prog. Polym. Sci., 26(5) 721-798, June 2001. 

The a-pyrone (635) undergoes an exothermic Diels-Alder reaction with 1-diethylamino-1-propyne to afford the cycloadduct (636) (77JOC2930). Only a single regioisomer is produced, which is in line with the expected polarization of these reagents (Scheme 144). A Diels-Alder reaction of the same a-pyrone with 1-dibenzylamino-l-propyne affords an aniline derivative which has been employed in a chiral synthesis of the aromatic portion of the ionophore antibiotic lasalocid (80JA6178). 

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