Propenylbenzenes anyone?

[psychokitty]

The PDF Documents in this post detail the synthesis of methyl(a-alkyl-)-styryl ketones via a condesation reaction between a benzaldehyde, an alkyl acetone, and HCl.  The subsequent application of sodium hypochlorite allows for the oxidation of the above intermediate to the a-alkylcinnamic acid, which can them be decarboxylated to form the even more desired a-alkylstyrene.  All of the intermediate products can easily be isolated and used without purification and the reaction can be scaled up without affecting yield.

The best example uses benzaldehyde (synthesized from either benzyl alcohol or toluene), MEK (methylethylketone; paint thinner), and HCl (muriatic acid) to form the intermediate methyl(a-methyl-)-styryl ketone, which can them be oxidized via NaOCl (Clorox) to a-methylcinnamic acid, and which can finally, of course, be decarboxylated to propenylbenzene.  Ring substitution doesn't appear to limit the reaction.

SOME ALPHA-ALKYLCINNAMIC ACIDS AND THEIR DERIVATIVES:

Physiologically Active Phenethylamines I. Hydroxy- and Methoxy-a-methyl-B-Phenethylamines (B-Phenylisopropylamines):

[psychokitty]

You guys like stuff to be hard because as far as I can tell, this synth is easy.  As for the decarboxylation step--assuming that propenylbenzene doesn't dimerize or decompose or whatever when in the presence of acids (HBr or H2SO4 in acetic acid) or bases or copper catalysts--the reactions detailed in the following PDF documents should do the trick:

Tetrahedron Letters 40 (1999) 6595-6598
Synthesis of styrenes through the decarboxylation of trans-cinnamic acids by plant cell cultures
Masumi Takemoto * and Kazuo Achiwa

Abstract
A new method has been developed for the synthesis of styrenes through the decarboxylation of trans-cinnamic acids by plant cell cultures at room temperature. 4-Hydroxy-3-methoxystyrene @I), 3-nitrostyrene (2d) and furan (2e) were synthesized quantitatively

On the Mechanism of Cinnamic Acid Decarboxylation in an Acid Medium
Walter W. Zajac, , Jr. Robert B. Nowicki;
J. Org. Chem.; 1966; 31(; 2712-2713.

J. Chem. Research (S), 2000, 42–43
Microwave enhanced decarboxylations of aromatic
carboxylic acids: improved deuteriation/tritiation
potential†
Lottie B. Frederiksen, Thomas H. Grobosch, John R. Jones*, Shui-Yu Lu and Chao-Cheng Zhao

Abstract:  Decarboxylation of aromatic carboxylic acids under microwave enhanced conditions is an increasingly attractive method of preparing deuterium/tritium labelled compounds.

FEMS Microbiology Letters 111 (1993) 245-250
Biodegradation of aromatic carboxylic acids by Pseudomonas mira
Marie Jurkovfi and Milan Wurst

Abstract: Biodegradation of aromatic acids (ferulic, vanillic and sinapinic acids) by the soil bacterium Pseudomonas mira was studied by high-pressure liquid chromatography. The presence of glucose in the culture medium slowed down the degradation process but did not affect its mechanism. In addition to vanillic acid and hydroquinone, the products of degradation were found to include acetophenone derivatives. Probably, a mechanism capable of shortening the side chain by spontaneous decarboxylation of unstable 3-keto-3-phenylpropionic acid was present, in addition to the elimination of acetic acid via degradation of the cinnamic acid-type compounds.

Substituted Styrenes. I. The Decarboxylation of Substituted Cinnamic Acids
Cheves Walling, Katherine B. Wolfstirn;
J. Am. Chem. Soc.; 1947; 69(4); 852-854.

The Acid-Catalyzed Decarboxylation of Cinnamic Acids
William S. Johnson, Walter E. Heinz;
J. Am. Chem. Soc.; 1949; 71(; 2913-2918.

Journal of the American Chemical Society 1 89:26 1 December 20, 1967
The Decarboxylation of p-Methoxy-P-methylcinnamic Acid. Solvent Isotope Effects and Acid Catalysis'
Donald S. Noyce, Leon M. Gortler, Fred B. Kirby, and Melvyn D. SchiavelW

Thermal Decarboxylation of Unsaturated Acids
Richard T. Arnold, Otto C. Elmer, R. M. Dodson;
J. Am. Chem. Soc.; 1950; 72(10); 4359-4361.

I'm sure there's even more information available out there somewhere.

The information in the following PDF document seems to suggest that sodium hypochlorite, under certain conditions , can effectively cleave the methylenedioxy ring structure

Tetrahedron Letters, Vol. 37, No. 7, pp. 1091-1094, 1996
Oxidation of Isosafrole by Sodium Hypochiorite Catalysed by Manganese Porphyrins: Unusual Competition between Epoxidation and O-Dealkylation
Luisella Bocchio Chiavetto, Gianfranco Guglielmetti, Cecilia Querci, and Marco Ricci*

[Sedrick]

Thanks. I'll have to look into this one. Nice mini archive of related documents here. I understand a source of HBr can be a bubbler that utilises KBr as the salt source. SWIM is not in a rush to start any new project at the moment but this work is appreciated none the less.

[Rhodium]

Psychokitty: Could you please add title/author/journal information to the above articles - I mean, how is anybody to find the above papers in TFSE when they are just unnamed links?

Also, to make people interested in a route you've found, it's very inefficient to just post a collection of PDF files - not many will open a dozen such files if they aren't described/advertised in some way.

[psychokitty]

From here on out, I'll try to be a bit more descriptive.

[java]

_Note: this were posted by psychokitty

Post 531053

(psychokitty: "Propenylbenzenes anyone?", Chemistry Discourse) added biography done only to make the article more searchable on the TFSE

Some Alpha-Alkylcinnamic Acids and their Derivatives
Marston Taylor bogert and David Davison
J. Am. Chem. Soc. Vol 54, 334-338, 1932

Introduction 
The phenomenal success of a-amylcinnamic aldehyde and other a-alkylcinnamic aldehydes as perfume bases, led us to prepare several of the corresponding methyl ketones (methyl- (a-alkyl-)-styryl ketones) .

These were synthesized by condensing benzaldehyde with alkyl acetones by means of hydrogen chloride. The methyl (a-alkyl-)-styryl ketones are readily converted to the a-alkylcinnamic acids by means of sodium hypochlorite. The acids, in turn, are of interest, since, through their dibromides  they may be transformed into the p-alkyl-0-bromostyrenes or into the alkylphenylacetylenes. The dibromides are also readily reconverted to the a-alkylcinnamic acids by means of potassium iodide.

Physiologically Active Phenethylamines. I. Hydroxy- and Methoxy-a-methyl-p Phenethylamines ( p-Phenylisopropylamines)
E. H. WOODRUFF AND THEODORE W. CONGER
Journal of the American Chemical Society  Vol. 60, No. 2, 465,1938

Excerpt.....the rediscovery of ephedrine by K. K. Chen in 1923 revived interest in the synthesis and pharmacology of p-phenethylamine and related compounds as evidenced by the increased number of publications appearing on the subject since that time. The fundamental principles regarding the chemical structure necessary for physiological activity, as well as the modifications in structure already investigated, are covered so thoroughly by extensive reviews in the l i t e r a t ~ r e ~ - ~ that any further discussion in connection with the work reported here is not considered necessary. Investigations covered in the reviews mentioned point to the presence of one or more hydroxyl groups in the benzene ring as one of the most potent modifiers of the magnitude of the physiological effects of compounds possessing the basic /3-phenethylamine skeleton.