3,3-Dimethylacryloyl chloride

Anisole and many of its derivatives react with an unsaturated acid chloride in the presence of aluminum chloride to yield a chromanone (20LA(42l)l). The two most widely used acid halides are but-2-enoyl (crotonyl) and 3-methylbut-2-enoyl (3,3-dimethylacryloyl) chlorides. In cases where the uncyclized intermediate, an acrylophenone, is isolated, cyclization may be achieved under acidic or basic conditions, or even simply by distillation (Scheme 220) (52G155). 

The usual range of solvents associated with Friedel-Crafts reactions is available carbon disulfide and nitrobenzene have found frequent use. The choice of solvent may influence the extent of cyclization. Thus, in ether, 1,2,3,5-tetramethoxybenzene yielded the uncyclized product with 3,3-dimethylacryloyl chloride, whereas in a mixture of ether and tetrachloroethane the major product was the chromanone. This example is also of interest since ring closure could involve either the 2- or 6-methoxy group. In fact, the formation of the 5,6,7-trimethoxy isomer was not observed. The identity of the product was established by conventional 14C labelling (60BSB593). 

Acyclic a,/3-unsaturated acid chlorides do not undergo this acylation. However, cyclic vinylsilanes also undergo Friedel-Crafts acylation with a,/S-unsaturated acid chlorides to give dienones of type a, which are cyciized by SnCl to cyclopentenones. A typical example is formulated for the reaction of 5-methyl-l-tri-methylsilylcyclopentene (3) with j3,iS-dimethylacryloyl chloride. The first step is conducted with AICI3 and gives 4, which after isolation is cyciized with SnCU to a mixture of 5 and 6. The cyclopentenone 6 is obtained in 55% overall yield after isomerization with RhCU. 

A complementary approach, developed by Paquette, - uses substituted acryloyl chlorides as addends in reaction with structii ly embellished vinylsilanes. A general route to the vinylsilanes (87) was found in the silylation of vinyllithiums generated by the Shapiro reaction.The acylation with acryloyl chlorides takes place readily with aluminum trichloride to afford the divinyl ketones which are subsequently cyclized with tin tetrachloride. The Nazarov cyclization products were formed as a mixture of double tend isomers (equation 47). The best results were obtained with p,p-dimethylacryloyl chloride. Crotonyl chloride could be employed, but acryloyl chloride proved impractical. This metl owes much of its utility to the regiocontroUed synthesis of Ae vinylsilmes, thereby clearly establishing the loci of cyclopentannulation. 

Kinetic studies of the alcoholysis of /3,/3-dimethylacryloyl chloride (49) with 14 alcohols in benzene at a reactant ratio of 1 1 have shown that the reaction probably proceeds via a charge-transfer complex. Reaction rates at high pressures (200, 500 and 1000 bar) of the reaction between a series of quinolines and benzoyl chloride in MeCN have been determined, together with those with 4-methyl- and 4-nitro-benzoyl chloride. Rate constants increased with increasing pressure, and it was concluded that those reactions proceed via an associative 5 n2 mechanism. ... 

The direct reaction of 2-trimethylsilylmethyl-1,3-butadiene with isovaleraldehyde gives ( )-ipsenol (2-methyl-6-methylene-7-octen-4-ol) in rather low yield (30%) (eq 5). However, ipsenol is obtained in 62% overall yield by the reaction of 2-trimethylsilylmethyl-1,3-butadiene with isovaleryl chloride, followed by reduction with diisobutylaluminum hydride (eq 7). Similarly, ( )-ipsdienol (2-methyl-6-methylene-2,7-octadien-4-ol) is obtained by reduction of myrcenone, prepared by the reaction of 2-trimethylsilylmethyl-1,3-butadiene with 3,3-dimethylacryloyl chloride, in 75% overall yield (eq 8). 

Also obtained by action of aluminium chloride with a mixture of hydroquinone dimethyl ether and 3,3-dimethylacryloyl chloride in boiling benzene for 3 h [3996]. 

Condensation of furfural aldehyde with (/ )-phenylglycinol gives an imine which is reduced with NaBH4 in isopropanol into amine 144 (Scheme 24). Temporary silylation of the primary alcoholic group of 144 as a trimethylsilyl ether and subsequent acetylation of the amine moiety with 3,3-dimethylacryloyl chloride... 

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