Diel migration

Roe, H.S.J., The diel migrations and distributions within a mesopelagic community in the North East Atlantic. 4. The copepods, Prog. Oceanogr., 13, 353, 1984. 

MIGRATION IN THE HYMENOLEPIDIDAE The migratory behaviour is even more complex in the case of the Hymenolepididae, in which the phenomenon has been extensively studied, especially in the case of Hymenolepis diminuta, by the fact that two interacting patterns of migration take place (20). One is an age-dependent forward migration and the other a diurnal (circadian, diel) migration. Since it is... 

F. Garcia-Pichel, M. Mechling, R.W. Castenholtz (1994). Diel migrations of microorganisms within a benthic, hypersaline mat community. Appl. Environ. Microbiol., 60,1500-1511. 

The Diels-Alder adduct 8 formed in a mixture with 7 by treatment of porphyrin 6 with dimethyl acetylenedicarboxylate undergoes a base-induced migration of a C —C double bond yielding a single diastereomer 9 with the thermodynamically favored tram arrangement of the methyl group and the methoxycarbonyl substituent.201... 

Acid catalyzed intramolecular Diels-Alder reactions in lithium perchlorate-diethyl ether acid promoted migration of terminal dienes prior to [4 + 2] cycioaddition in conformationally restricted substrates [101]... 

The Lewis acid-catalyzed 1,3-migration of divinyl esters allows the formation of 1,3-butadienes, which can undergo cycloaddition. In this respect, Dai and coworkers described a rearrangement of the divinyl alkoxyacetate 1-203 followed by a Diels-Alder reaction with a dienophile such as maleic anhydride 1-204 in the presence of catalytic amounts of Ln(fod)3 to produce 1-205 in up to 61 % yield (Scheme 1.47) [53],... 

Details of various routes to allylphosphine oxides (43) have been reported, and the subsequent synthesis of 1,3-dienes has been illustrated by many examples.37 Also described are stereochemical aspects of these diene syntheses and of subsequent Diels-Alder cycloaddition reactions.37 High regioselectivity is observed in migrations of the diphenylphosphinoyl group from unsymmetrical sites, as in (44), in that both products have a double bond exocydic to the cyclohexane ring.38... 

The interplay of crystal packing, migrational aptitudes, and solid-state reactivity maybe demonstrated with the reactivities of the Diels-Alder cycloadducts of maleic anhydride and cyclopentadiene (1 and 2) or cyclohexadiene (3). 

The authors proposed mechanism for dimerization involves initial formation of metal vinylidene complex 9 via 1,2-H-migration. A second molecule of arylacetylene acts as a dienophUe in a formal [4 + 2] Diels-Alder cycloaddition with 9. A subsequent... 

METHOXYCARBONYL-1,1,6-TRIMETHYL-1,4,4a,5,6,7,8,8a-OCTAHYDRO-2,3-BENZOPYRONE, an intramolecular Diels-Alder reaction is responsible for the diastereoselectivity. The stereoselective 1,4-functionalization of 1,3-dienes is exemplified by a two-step process leading to cis- and trans-1-ACETOXY-4-(DICARBOMETHOXYMETHYL)-2-CYCLOHEXENE. The effectiveness of a silyl hydride in providing a means for erythro-directed reduction of a p-keto amide is applied in a route to ERYTHRO-1 -(3-HYDROXY-2-METHYL-3-PHENYL-PROPANOYLJPIPERIDINE. This is followed by an asymmetric synthesis based on a chiral bicyclic lactam leading to (R)-4-ETHYL-4-ALLYL-2-CYCLOHEXEN-1-ONE. The stereoselectivity with which acetoxy migration can operate to an adjacent radical center is reflected in the one-step reaction that gives rise to 1,3,4,6-TETRA-O-ACETYL-2-DEOXY-a-D-GLUCOPYRANOSE. 

It has been suggested307 that the observed thermal rearrangement of the bicyclo[2.2.2]- to the bicyclo[3.2.1]-octadiene skeleton in tricyclic lactams, viz. (265)—>-(266), is consistent with an intramolecular Diels-Alder reaction in which a zwitterion is formed by the migration of one vinyl group from C(l) to C(5) of the lactam moiety (see Scheme 62). It has been shown308 that the 7r-facial selectivity of the Diels-Alder reaction of 1,3-dienes (267) having an attached stereogenic centre can be... 

The reaction of /V-cyclohexyl-/V-(2-pyridyl)carbodiimide and the allenic acid 83 in dry tetrahydrofuran at ambient temperature for 3 days afforded a 2 1 mixture of isomeric 2-oxo-2H- and 4-oxo-4/7-pyrido[l,2-a]pyrimid-ines 88 and 87 instead of the expected Diels-Alder adduct (92HCA1262). The formation of an activated ester 84 was suggested in the first step, which underwent a 1,5- or 1,3-acyl migration, giving rise to the isomeric pyrido(l,2-a]pyrimidines 87 and 88 via acylureas 85 and 86, respectively (Scheme 6). 

As mentioned in Scheme 7.3, although thermal ene reaction of the 1,6-enyne 320 gives only 1,4-dienes 324, the 1,3-diene 325 is formed by the Pd-catalysed reaction. No thermal ene reaction is possible with 342, but the smooth Pd-catalysed cyclization affords the 1,3-diene system 343, which has a skeleton analogous to 325 in Scheme 7.3. Notably, the reaction proceeds with migration of vinylic hydrogen. The 1,3-diene system formed by the cyclization is useful for further modification, typically Diels-Alder reaction. The 1,3-diene 343 formed from 342 is converted to sterepolide (344) by Diels-Alder reaction [140]... 

---