3-Norcarenes

Rearrangement of polycyclic systems. (4, 432-435 5,585-587). Paquette has reviewed shver ion-catalyzed rearrangements of cyclic systems, particularly those that are useful synthetically. A few of these are formulated. One is the preparation of homotrophidene (2) from 3-norcarene (1) shown in equation I. Note that rearrangement of (3), with a methyl group at a bridgehead position. 

Norcarene, 68, 518 21-Norconanine, 72 Norpinene, 455 19-Norsteroids, 411 Nortricyclene, 232 Nuciferal, 461... 

Norcarene, 3,7,7-trimethyl- 3,7,7-Trimethylbicyclo [4.1.0] hept-3-ene 4,7,7-Trimethyl-3-norcarene... 

Norcarene, 3,7,7-tri methyl-. See 3-Carene Norcast 140-1, Norcast 141, Norcast 142... 

Trimethyl-3-norcarene. See 3-Carene N,N,N-Trimethyl-1 -octadecanaminium chloride. 

A simple conversion of 3-norcarene into trans-bishomobenzene has been discovered. The method involves reaction of (693), itself obtained in two standard steps from 3-norcarene, with Bp3,OEt2. Silver perchlorate-catalysed decomposition of (693) gave 2,3-homotropilidene quantitatively. 

Since the norcarene intermediate 34 has a double bond in the 6-membered ring, a Diels-Alder cycloreversion leading to cyclopropene (35) and butadiene is also a possible disconnection. The corresponding synthetic sequence has been carried out in the laboratory in 37% yield [32] ... 

Tropones are obtained in good over-all yields when the dihalocarbene adducts of A2- and A3-norcarenes are first allylically oxidized and the resulting ketones subsequently subjected to a dehydrohalogenation sequence [136]. 

Rule 8. Form -ene (one double bond) and -diene (two double bonds) names according to Rule 4 above, and write the bicyclo and nor- names as solid words — e.g., bicycloQ3.1.0 hex-2-ene, norcarene, and norpinadiene. 

The position numbers for point or points of attachment, double bonds, and substituents in the nor- names will be identical to those in the corresponding systematic bicyclo names. Examples 4-norcaren-2-yl is synonomous to bicyclo 3 [4.1.0 ]hept-4-en-2-yl l,3,3-trimethyl-2-norbornyl to 1,3,3-trimethylbicyclo 3 [2.2.l]hept-2-yl 3,3 dimethyl-2-norbornylidenemethyl to 3,3-dimethylbicyclo3 [2.2.1 ] hept-2-y lidenemethyl. 

In unsaturated radical names, the position number or numbers designating the point or points of attachment will precede the distinguishing ending of the radical name Examples 3-thujen-7-yl, 3(10>-caren-2-yl, 4-norcaren-2-yl, 2-pin en-10-yl, 2(10),3-pinadien-3-yl, 2,5-bomadien-2-yl, -norbomen-2-yl l-isopropenyl-4-methylbicyclo[3.1 0]hex-3-en-2-yl. 

Several norcarene derivatives were shown to undergo dehydrogenation with ring opening to form the more extended % system of cycloheptatriene. Thus, irradiation of chloranil in the presence of tricyclo[4.4.1.016]undeca-3,8-diene (45) gave rise to bicyclo[4.4.1]undeca-l,3,6-8-tetraene (46), while the quinone was reduced to the corresponding hydroquinone [229, 230]. 

Norcarene (92) is photochemically reactive by both direct and triplet-sensitized irradiation. Direct irradiation at 214 nm affords the products shown in Scheme 6, and the reaction path was studied in detail by the use of deuterium-labelled compounds. Under sensitized conditions, two products were formed (Scheme 7). The authors reason that it is difficult to differentiate between concerted and biradical paths for product formation, owing to the... 

CIDNP effects observed for norcarene [147, 178] supported a radical cation, 87 +, which spin and charge are delocalized between the olefinic group and the Walsh orbital of the (more highly substituted) internal cyclopropane bond. The bicyclo-heptene system, 87 +, appears to be more flexible than 86 + either the internal or the lateral cyclopropane bond can align with the alkene p-orbitals. Delocalization of spin and charge into the more highly substituted bond is preferred. 

In contrast to the singlet photobehaviour generally observed for aliphatic cyclopropanes, the product mixture observed upon direct irradiation (214 nm, pentane solution) of 2-norcarene (37) reveals that this system is unusual in many respects (equation 28) . 

Certain of the bridged A -norcarenes depicted by 149, and formed by [2-1-4] cycloaddition, rearrange to cycloheptadienes or -trienes under the reaction conditions . For example, tetrachlorocyclopropene and cyclopentadiene give 153 in 95% yield by facile two-electron disrotatory cyclopropyl-allyl opening of the primary [2 -H 4] endo adduct (equation 57). The cycloadditions of simple cyclopropenes with dienes such as... 

The configurations of these hydroxy acids were assigned by NMR spectroscopy and comparison with the data of some alkylated cyclopropanecarboxylic acids and 1-hydroxycyclo-propanecarboxylic acids. Chemical evidence for the exo configuration of the carboxy group and endo configuration of the hydroxy group resulted from the preparation and reaction of a norcarene-7-carboxylic acid, i.e. the 7-hydroxy-cw-bicyclo[4.1.0]hept-3-ene-exo-7-carboxylic acid (10a). 

When oxidizing agents are used additional activation is not required thus, lead(lV) acetate reacted with a 2-methylprop-l-enyl group by concomitant oxidation and rearrangement and a 2-norcarene derivative reacted similarly with selenium dioxide. Rearrangement accompanied by oxidation also occurred on reaction of derivatives of tricyclo[3.2.1.0 ]oct-6-en-8-one with potassium rert-butoxide in dimethyl sulfoxide. " ... 

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