Pentyn--one

Acetylenic alcohols can be converted into ketones in good yield and without side reactions by means of chromic-sulfuric acid in acetone for example, 3-pentyn-2-ol gives 3-pentyn-2-one smoothly at 5-10°.435 Mild oxidation of various steroids and terpenes has been achieved by this procedure.436... 

The photochemical addition of a,jS-acetylenic ketones with alkenes yields acid-sensitive products In the absence of acids, reaction of 3-pentyn-2-one with tetramethylethylene... 

Sensitive ketones such as 3-pentyn-2-one also afford the corresponding vinyl triflate on treatment with Tf20 in the presence of a base (eq 18). ... 

The irradiation of 2,5-dimethylfuran in the presence of mercury vapor gave a complex mixture of products. Carbon monoxide and propene were removed as gaseous products. Then, cis- and rran.s-l,3-pentadiene, isoprene, 1,3-dimethylcyclopropene, 2-pentyne, 2-ethyl-5-methylfuran, hexa-3,4-dien-2-one, 1-methyl-3-acetylcyclopropene, and 4-methylcyclopent-2-enone were obtained (Scheme 8) (68JA2720 70JA1824). The most abundantproduct was the cyclopentenone 19, the second was the 1,3-pentadiene 12, while the third product was the cyclopropenyl derivative 18. 

The dinuclear isonitrile and alkoxycarbene complexes 6 and 7 were obtained from [Fe(CO)3( X-dppm) Tl2- j,2-Si(OMe)2(OMe))PtCl] by chloride substitution with isonitriles and 3-butyne-l-ol (or ( )-4-pentyne-2-ol), respectively [2], In these complexes, the organic ligand bound to Pt only occupies one coordination site, thus allowing the trimethoxysilyl ligand to display a T 2- i2-Si-0 bonding mode. 

Show how the following compounds can be prepared, using ethyne as one of the starting materials. Explain why ethyne should be alkylated before, rather than after, nucleophilic addition, a. l-pentyn-3-ol b. l-phenyl-2-butyn-l-ol c. 2-methyl-3-hexyn-2-ol ... 

One way to avoid this is to have a mixed copper reagent (2) in which R is preferentially transferred to the cnonc. A good choice for R is an acetylene and the preferred acetylene is 1-pentyne (3) as it is cheap, easy to make, and reasonably volatile. 

In only one case was the triple bond differently functionalized a terminal acetylene group was converted by hydroboration into a for-mylmethylene (OHC-CH2-) grouping. In this way, 2-deoxy-DL-erythro-pentose (2) was obtained10 from en/t/iro-4-pentyn-l,2,3-triol (1). 

Suppose you were given unlabeled bottles, each of which is known to contain one of the following compounds 1-pentanol, 2-pentanol, 2-methyl-2-butanol, 3-penten-1-ol, 4-pentyn-1-ol, 1-butoxybutane, and 1-pentyl acetate. Explain how you could use simple chemical tests (test-tube reactions only) to identify the contents of each bottle. 

A catalytic, completely regioselective conversion of 4,4-dimethyl-2-pentyne (methyl-r-butylacetylene) to 2,5-di(r-butyl)-3,4-dimethylcyclopentadienone is mediated by (PhCN)2PdCl2. Other examples exist for early as well as late transition metals, and an isonitrile has been used as a CO equivalent in one Ni -based system as well, Finally, a heterogeneous catalytic intramolecular cycloaddition of diynes has been developed, leading to cyclopentadienones which either dimerize (Diels-Alder) or in certain cases may be trapped by nucleophiles (equation 10). °... 

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