3- Chloro-3-methyl-l-butyne

Some synthetically important allenylmetallics, such as allenylzinc and allenylin-dium reagents, are prepared from allenylpalladium intermediates. These reactions are discussed in appropriate sections of this chapter. This section covers the reactions of allenylpalladium compounds without further transmetallation. Allenylpalladium complexes can be prepared from propargylic halides, acetates, carbonates, mesylates, alcohols and certain alkynes [83-87], The allenylpalladium compound prepared from 3-chloro-3-methyl-l-butyne has been isolated and characterized spectroscopically (Eq. 9.106) [83], It was found to couple with organozinc chlorides to produce homologated allenes quantitatively (Eq. 9.107). 

Chloro-3-methyl-l-butyne from the Corresponding Carbinol and Concentrated HCI... 

Formylation of 5,7-dihydroxy -( -propyl)-coumarin (1) provided on 8-formy-lated product (26). Treatment of the compound 26 with 3-chloro-3-methyl-l-butyne to introduce regioselectively the chromene 27 because the phenolic hydroxyl group at the C position was less accessible for formylated substitution because of a presumed hydrogen-bonding interaction. To construct the enantiomerically pure rra i-2,3-dimethyl chroman-4-ol system, Deshpande et al." ° used organoborone... 

Chloro-3-methyl-l-butyne, 916 2-Chloro-2-methyl-3-butyne, 916 2-Chloro-2-methylcyciohexanoae, 609,1128 N-2-Chloromethyl-0,N-dimethylhydroxyl-amine, 1078... 

A one-step synthesis of this alkaloid is consequent upon the reaction of thallous salts of nonchelated j8-diketones with alkyl halides. In the present instance the thallous salt of 4-hydroxyquinolone (93) reacted with 3-chloro-3-methyl-l-butyne to generate flindersine (94) in 28% yield 111). 

Similar conclusions have been drawn from the effects of hydrostatic pressure on the solvolysis of 3-chloro-3-methyl-l-butyne . The activation volume of the neutral solvolysis is —15 cm. mole, in close agreement with the values observed for /-alkyl halides. The net effect of pressure on the base-promoted reaction is remarkably small (AK =-H2cm mole ). The most reasonable interpretation is that the departure of chloride ion is accompanied by the creation of another pair of charges, i.e. the zwitterion-carbene. 

The reagent is prepared by reaction of 3-chloro-3-methyl-l-butyne with methyl-lithium in ether at -75°. ... 

An ethereal soln. of 3-chloro-3-methyl-l-butyne added dropwise with stirring at 17-20° under N2 to a mixture of piperidine, ether, water, and small amounts of both GuGl and Gu-bronze, stirring continued 2 hrs. at room temp. 3-pi-peridino-3-methyl-l-butyne. Y 68%. F. e. and methods s. G. F. Hennion and R. S. Hanzel, Am. Soc. 82, 4908 (1960). 

A number of unsaturated carbenes have been generated under phase transfer conditions. The most extensive work has been reported for dime thy Ivinylidene carbene. Dimethylvinylidene carbene has been generated by base catalyzed 7-elimination of HCl from 3-chloro-3-methyl-l-butyne and by a-elimination of HBr from l-bromo-3-methyl-1,2-butadiene (see Eq. 4.13). Both quaternary alkylammonium salts and various crown ethers have proved to be effective catalysts for this reaction. Yields of dimethylvinylidenecyclopropane products obtained under phase transfer catalytic... 

COCH3 Obtained by tnealment of 2,4-dihydroxy-5-methoxy-acetophenone with 3-chloro-3-methyl-l-butyne in the presence of potassium carbonate and potassium iodide in DMF for 40 h at 80-85° (15%) [3544], Yellow oil [3544] TLC [3544] >H NMR [3544], UV [3544]. 

Three different types of reagents have been used for the alkylation of 1,3-dioxyacridones and subsequent construction of the fused dimethylpyran D ring of pyranoacridone alkaloids. l-Halo-3-methyl-2-butenes enable cyclization to a dihydrodimethylpyran ring, and dehydrogenation or oxidation has to take place in the course of the synthesis, in order to obtain the desired pyranoacridone. In contrast, the use of the tertiary alcoholic 3-hydroxyisovaleraldehyde dimethylacetal and of the acetylenic 3-chloro-3-methyl-l-butyne permit direct cyclization to the required dimethylpyran. 

A second route involved the intermediacy of benzophenone 351. Treatment of 3,5-dimefhoxyphenol (354) with 3-chloro-3-methyl-l-butyne (278) gave 5,7-dimethoxy-2,2-dimethylcln omene (359), which could be regioselectively lithiated at the 6-position by use of butyllithium in ether. Reaction of the lithio derivative 360 with 2-methyl-3,l-benzoxazin-4-one (255) smoothly afforded the required aminobenzophenone 351. Cyclization with sodium hydride in dimethylsulfoxide occurred with simultaneous loss of the acetyl group, to give 12-... 

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