I -octyne

Distil I-octyne from NaBH4 to remove peroxides. Fractionate it through a lOinch Widmer column (p 11) at 125-126°/759mm [Sletzinger Dawson J Org Chem 14 853 1949.] [Beilstein 1 III 1005,1IV 1034.]... 

Let s start with a synthesis of racemic S-deoxy-VGEi (90) developed by the Sih group at the University of Wisconsin. The key reaction was the addition of vinyllithium 88 to the THP ether derived from enone 86. The vinyllithium reagent was prepared by hydroalumination-iodination of I-octyne (87) followed by a transmetallation. Enone 86 was prepared in two steps from cyclopentadiene and ethyl 7-bromoheptanoate. Notice that the alkylation of lithium cyclopentadienide with this bromoester provided I-substituted cyclopentadiene 84 in quantitative yield. The isomerization that had to be avoided in the Corey lactone approach was a necessary part of these tactics. 

J-unsaturated ester is formed from a terminal alkyne by the reaction of alkyl formate and oxalate. The linear a, /J-unsaturated ester 5 is obtained from the terminal alkyne using dppb as a ligand by the reaction of alkyl formate under CO pressure. On the other hand, a branehed ester, t-butyl atropate (6), is obtained exclusively by the carbonylation of phenylacetylene in t-BuOH even by using dppb[10]. Reaction of alkynes and oxalate under CO pressure also gives linear a, /J-unsaturated esters 7 and dialkynes. The use of dppb is essen-tial[l 1]. Carbonylation of 1-octyne in the presence of oxalic acid or formic acid using PhiP-dppb (2 I) and Pd on carbon affords the branched q, /J-unsatu-rated acid 8 as the main product. Formic acid is regarded as a source of H and OH in the carboxylic acids[l2]. 

Finally, the only example of a polynuclear homogeneous catalyst is the dinuc-lear complex [Pt P sH ]4- [66], which catalyzed the hydrogenation of styrene, phenylacetylene, 1-octyne, and 1-hexyne (i-PrOH, 60°C, 20.7 atm H2 pressure, Pd substrate ratio 1 1800) to the corresponding alkanes within 10 h of reaction. 

The combination of [IrCl(cod)Cl]2 complex with P(t-Bu)3 efficiently catalyzes aromatic homologation using internal alkyne [70]. For example, the reaction of benzoyl chloride 153 with 4-octyne 154 afforded 1,2,3,4-tetrapropylnaphthalene 155 (Equation 10.41). The reaction with 2-thenoyl and 2-naphthoyl chlorides also affords benzothiophene and anthracene, respectively, in high yields. The reaction would proceed as follows (Scheme 10.9) (i) oxidative addition of aroyl chloride... 

A solution of 0.30 mol of octynylmagnesium bromide in - 300 ml of THF is prepared starting from 0.35 mol of ethyl bromide and 0.30 mol of 1-octyne (for the procedure see p. 29). Powdered copper(I)chloride (2 g, technical grade) is added at room temperature. After 15 min... 

The study of Tables I and II has revealed the fact that isomerization of a normal paraffin to an isoparaffin produces certain specific and characteristic changes in the physical constants as the methyl group is moved from point to point along the chain. In a paper presented before the Refining Division of the American Petroleum Institute in November 1942, attention was called by this author to alternation in the melting points of the n-octenes and n-octynes as the point of unsaturation is moved from position 1 to 2 to 3 to 4 (5). Now that the cis-trans pairs have been separated and more highly purified, the alternation remains characteristic of both forms, although the data on the cis forms are not fully verified. 

Bromoboration (Z)-/>2-dihalo-l -alkenes1 Reaction of a terminal alkyne (1 -octyne) with BBr3 in CH2C12 results in a p-bromoalkenylborane, which undergoes brominolysis or iodinolysis with retention to provide (Z)-l,2-dihalo-l-alkenes (equation I). 

Although the silylformylation of aldehydes is catalyzed by [Rh(COD)Cl]2 or [Rh(CO)2Cl]2, no secondary silylformylation of /i-silylenals (316-318) takes place, probably due to the electronic nature of the aldehyde functionality conjugated to olefin moiety (vide supra). Direct comparison of the reactivity of acetylene and aldehyde functionalities is performed using alkynals328. The reactions of 5-hexyn-l-al, 6-heptyn-l-al and 7-octyn-l-al with different hydrosilanes catalyzed by Rh or Rh—Co complexes at... 

AUyUdumination of alkynes.4 The reaction of allyldiisobutylaluminum, prepared from allylmagnesium bromide and i-Bu2A1C1, with 1-octyne in the presence of Cl2ZrCp2 results in ds-allylalumination to provide a mixture of two regioisomers, 1 and 2. Internal... 

This thermal addition is usually sluggish below 120 C (e.g. for 1-octyne 140 (i, 5 h, 42% adduct 120 (1, 5 h, 11% 100°C, 5 h, 3%). Interestingly, the reaction with phenylacetylene occurs on heating even at 80 °C (76% of the desired adduct). The high reactivity of phenylacetylene is probably because vinyl radicals bearing a phenyl group at the a position of the radical center form Ti-radicals and are more stable than usual vinyl radicals, which are <7-radicals (Scheme 15.62) [142]. 

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