B15 2TTU.V. irradiation of 6-acetoxy-2,3,4,5.6-pentamethylcyclohexa-2,4-dienone in ether or methanol gives exo-6-acetoxy-I , 3,4,5.6-pentamethylbicyclo[3,1 ,O] hex-3-en-2-0ne. whose structure i s established by degradation to tetramethylcyclopent-2-enone derivatives. Low-temperature spectroscopy and trapping experiments s how the dienone to suffer stereospecific photochemical ring opening to a keten, which can be trapped by cyclohexylamine, and may isomerise to the bicyclohexenone in a stereospecific thermal bond-crossing reaction, or to the dienone by a thermal and probably also a photochemical reversion. The latter processes are strongly solvent-dependent.IN the preceding paper1 we showed that a 6-acetoxypent a-a1 kylcyclohexa-2,4-dienone undergoes pho torearrangement to a bicyclo[3,1 ,O] hex-3-en-2-one by a highly stereoselective skeletal rearrangement. We now consider in more detail the analogous rearrangement of 6ace t ox ypent ame t hylcyclohexa-2,4-dienone (pentamethyl-o-quinol acetate) (I).The quinol acetate (I) was made by lead tetra-acetate acetox ylation of pent ame t hylphenol in chloroform .z I t has been reported to be obtained from a similar reaction in acetic acid.3 U.V. irradiation, through Pyrex glass, in dry or wet ether, or methanol solution, and isolation by careful crystallisation gave up to 80% of photoproduct (11). Analysis by g.1.c. of the crude photomixture from irradiations in wet ether indicated a yield of (11) greater than 70% at 907; conversion, but is complicated by the finding that (I) undergoes partial thermal rearrangement to its Pam-isomer (111) 7 under .i. Dienone (111) was prepared by acid-catalysed isoinerisation of '(I) (see Experimental section). It was previously obtained in the preparation of (I).3 the g.1.c. conditions used. The volatile impurities are pentamethylphenol, unchanged quinol acetate, and two unidentified products (ca. 476). Analyses by n.m.r. 1
The Photorearrangement of 6-Acetoxy-3,5-bis(chloromethyl)-2,4,6-trimet hylcyclo hexa-2,4-d ienone By M. R. Morris and A. J. Waring," Chemistry Department, University of Birmingham, P.O. Box 363, Birmingham B15 2TT U.V. irradiation of 6-acetoxy-3,5-bis(chloromethyl)-2,4,6-trimethylcyclohexa-2,4-dienone causes its highly stereoselective rearrangement to exo-6-acetoxy-I ,4-bis( chloromethyl) -3.5,6-trirnethylbicyclo[3.1 ,O] hex-3-en-2one. This readily eliminates acetyl chloride to give a 5-methylenecyclopent-2-enone. These results help to establish the overall mechanism of the photoisomerisation of heavily substituted cyclohexa-2.4-dienones to bicyclo [3,1 ,O] hex-3-en-2-ones.
ObjectivesHow brain MRI lesions associate with outcomes in pediatric anti-NMDA receptor encephalitis (pNMDARE) is unknown. In this study, we correlate T2-hyperintense MRI brain lesions with clinical outcomes in pNMDARE.MethodsThis was a multicenter retrospective cohort study from 11 institutions. Children younger than 18 years with pNMDARE were included. One-year outcomes were assessed by the modified Rankin Score (mRS) with good (mRS ≤2) and poor (mRS ≥3) outcomes.ResultsA total of 175 pNMDARE subjects were included, with 1-year mRS available in 142/175 (81%) and 60/175 (34%) had abnormal brain MRIs. The most common T2-hyperintense lesion locations were frontal, temporal, and parietal. MRI features that predicted poor 1-year outcomes included abnormal MRI, particularly T2 lesions in the frontal and occipital lobes. After adjusting for treatment within 4 weeks of onset, improvement within 4 weeks, and intensive care unit admission, MRI features were no longer associated with poor outcomes, but after multiple imputation for missing data, T2 frontal and occipital lesions associated with poor outcomes.DiscussionAbnormal frontal and occipital lesions on MRI may associate with 1-year mRS in pNMDARE. MRI of the brain may be a helpful prognostication tool that should be examined in future studies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.