Lewis Base-assisted Arylation of Unsaturated Carbonyls

The combination of Lewis bases with α,β-unsaturated carbonyls allows the in-situ generation of enolates without the need for strong Brønsted bases. Recently developed synthetic methods employ this approach for arylation followed by elimination of the Lewis base, regenerating the alkene. This strategy has been deployed for formal α- or β-C-H arylation in different contexts, namely (a) transition metal catalysis, (b) rearrangement reactions utilizing hypervalent main group elements and (c) organocatalysis. This concept article provides an overview of the developed strategies, highlighting and contextualizing their features.

Synthese von α-Arylacrylamiden via Lewis Base vermitteltem Aryl/Wasserstoff-Austausch

Hierin stellen wir eine neue Methode für die Synthese von α‐Arylacrylamiden vor. Die Reaktion basiert auf der Nutzung polarer S‐zu‐C Arylwanderungen, induziert durch einen Lewis‐basischen Organokatalysator. Im Unterschied zu zuvor publizierten radikalischen Arylwanderungen von Sulfonylacrylamiden, ermöglicht dieser polare Prozess eine darauffolgende Eliminierung, wodurch in Summe ein formaler Aryl/Wasserstoff‐Austausch unter Ausscheidung von SO2 stattfindet. Die vorgestellte Reaktion ist selektiv für elektronenarme aromatische Gruppen, während eine Vielfalt von Substituenten am Stickstoff und an der β‐Position toleriert werden, und erzeugt nützliche Bausteine für Folgereaktionen wie Zykloadditionen und Zyklisierungen. Der Reaktionsmechanismus wurde mithilfe quantenchemischer Berechnungen erforscht, die die unerwartete Rolle der Lewis Base in mehreren Schlüsselschritten darlegten.

Synthesis of α-Aryl Acrylamides via Lewis-Base-Mediated Aryl/Hydrogen Exchange

Herein we report a method for the synthesis of α-aryl acrylamides leveraging polar S-to-C aryl migrations induced by a Lewis basic organocatalyst. In contrast to previously reported radical aryl migrations of sulfonyl acrylimides, this polar process enables subsequent elimination, ultimately leading to a formal aryl/hydrogen exchange including SO₂ extrusion. This reaction is selective for electron-deficient aromatic groups, while tolerating a variety of substituents on nitrogen and in the β-position, and it delivers useful building blocks for further transformations, including cycloaddition and cyclisation reactions. The mechanism was investigated in detail using quantum chemical calculations, which unexpectedly revealed the Lewis base to be involved in several decisive steps.

HFIP Mediates a Direct C-C Coupling between Michael Acceptors and Eschenmoser's salt

A direct C-C coupling process merging Michael acceptors and Eschenmoser's salt is presented. Albeit reminiscent of the Morita-Baylis-Hillman reaction, this process requires no Lewis base catalyst. The underlying mechanism could be unveiled by a combination of kinetic, isotopic labelling experiments as well as computational investigations, showcasing the critical role of HFIP as a superior mediator for proton transfer events as well as the decisive role of the halide counterion.

Chemoselektive γ-Oxidation von β,γ-ungesättigten Amiden mit TEMPO

Ein chemoselektives und robustes Protokoll zur γ‐Oxidation von β,γ‐ungesättigten Amiden wird dargelegt. Bei dieser Methode ermöglicht elektrophile Amidaktivierung eine bei ungesättigten Amiden bisher selten angewendete regioselektive Reaktion mit TEMPO, die zu γ‐aminoxylierten α,β‐ungesättigten Amiden führt. Radikalische Zyklisierungen und Oxidationen der synthetisierten Produkte untermauern die Nützlichkeit der hergestellten Verbindungen.

Chemoselective γ-Oxidation of β,γ-Unsaturated Amides with TEMPO

A chemoselective and robust protocol for the γ‐oxidation of β,γ‐unsaturated amides is reported. In this method, electrophilic amide activation, in a rare application to unsaturated amides, enables a regioselective reaction with TEMPO resulting in the title products. Radical cyclisation reactions and oxidation of the synthesised products highlight the synthetic utility of the products obtained.

Prophylactic salpingectomy for prevention of ovarian cancer at the time of elective laparoscopic cholecystectomy

Background

Most serous ovarian cancers are now understood to originate in the fallopian tubes. Removing the tubes (salpingectomy) likely reduces the risk of developing high‐grade serous ovarian cancer. Numerous gynaecological societies now recommend prophylactic (or opportunistic) salpingectomy at the time of gynaecological surgery in appropriate women, and this is widely done. Salpingectomy at the time of non‐gynaecological surgery has not been explored and may present an opportunity for primary prevention of ovarian cancer.

Methods

This study investigated whether prophylactic salpingectomy with the intention of reducing the risk of developing ovarian cancer would be accepted and could be accomplished at the time of elective laparoscopic cholecystectomy. Women aged at least 45 years scheduled for elective laparoscopic cholecystectomy were recruited. They were counselled and offered prophylactic bilateral salpingectomy at the time of cholecystectomy. Outcome measures were rate of accomplishment of salpingectomy, time and procedural steps needed for salpingectomy, and complications.

Results

A total of 105 patients were included in the study. The rate of acceptance of salpingectomy was approximately 60 per cent. Salpingectomy was performed in 98 of 105 laparoscopic cholecystectomies (93·3 per cent) and not accomplished because of poor visibility or adhesions in seven (6·7 per cent). Median additional operating time was 13 (range 4–45) min. There were no complications attributable to salpingectomy. One patient presented with ovarian cancer 28 months after prophylactic salpingectomy; histological re‐evaluation of the tubes showed a previously undetected, focal serous tubal intraepithelial carcinoma.

Conclusion

Prophylactic salpingectomy can be done during elective laparoscopic cholecystectomy.

Unified Approach to the Chemoselective α-Functionalization of Amides with Heteroatom Nucleophiles

Functionalization at the α-position of carbonyl compounds has classically relied on enolate chemistry. As a result, the generation of a new C–X bond, where X is more electronegative than carbon requires an oxidation event. Herein we show that, by rendering the α-position of amides electrophilic through a mild and chemoselective umpolung transformation, a broad range of widely available oxygen, nitrogen, sulfur, and halogen nucleophiles can be used to generate α-functionalized amides. More than 60 examples are presented to establish the generality of this process, and calculations of the mechanistic aspects underline a fragmentation pathway that accounts for the broadness of this methodology.

Synthesis, Structure, and Reactivity of Binaphthyl Supported Dihydro[1,6]diazecines

A short approach to chiral diaza-olefines from protected 2,2'-diamino-1,1'-binaphthyl is presented. Cis- and trans-olefines can be selectively obtained by twofold N-allylation followed by RCM or by bridging a 2,2'-diamino-1,1'-binaphthyl precursor with trans-1,4-dibromo-2-butene. Deprotection afforded cis- and trans-dihydro[1,6]diazecines 1 in 58 and 64% overall yield. The reactivity of the but-2-ene-1,4-diyl fragment was investigated yielding corresponding epoxides, diols, and mono- and dibromo products. In several cases rearrangements and participation of the proximate N-Boc group was observed. In no case could allylic substitution be accomplished. From 13 compounds X-ray structure analyses could be obtained.

Amide activation: an emerging tool for chemoselective synthesis

It is textbook knowledge that carboxamides benefit from increased stabilisation of the electrophilic carbonyl carbon when compared to other carbonyl and carboxyl derivatives. This results in a considerably reduced reactivity towards nucleophiles. Accordingly, a perception has been developed of amides as significantly less useful functional handles than their ester and acid chloride counterparts. However, a significant body of research on the selective activation of amides to achieve powerful transformations under mild conditions has emerged over the past decades. This review article aims at placing electrophilic amide activation in both a historical context and in that of natural product synthesis, highlighting the synthetic applications and the potential of this approach.

Regioselective synthesis of pyridines by redox alkylation of pyridine N-oxides with malonates

ABSTRACT

A regioselective synthesis of pyridines by the addition of malonate anions to pyridine N-oxide derivatives, which have been activated by trifluoromethanesulfonic anhydride, is reported. The reaction selectively affords either 2- or 4-substituted pyridines in good yields.

GRAPHICAL ABSTRACT

Management of pancreatic trauma and its consequences--guidelines or individual therapy?

BACKGROUND/AIMS

Diagnosis of pancreatic trauma and its complications may be difficult due to non-specific signs and symptoms and treatment recommendations are not unequivocal.

METHODOLOGY

Clinical data of a series of 47 patients with pancreatic trauma were analyzed; most of them were polytraumatized and treated by an interdisciplinary team.

RESULTS

The most common causes were traffic accidents and sport injuries with 66% and 15%, respectively. Concomitant injuries were seen in 96% (nonpancreatic intra-abdominal injuries 85% including spleen 38% and liver 34%, extra-abdominal injuries 70%). Concomitant liver injuries were treated conservatively in 31% and operatively in 69% (including hepatic packing in 38%). Concomitant splenic injuries were usually very severe and could be managed conservatively in only 11%. All patients with pancreatic injuries grade III, IV or V (17%) according to the American Association of Surgical Trauma Classification required surgery, endoscopic treatment or interventional radiology. The most common posttraumatic complications were necrotizing pancreatitis (15%), pseudocyst formation (9%), abscesses (6%) and fistulas (4%).

CONCLUSIONS

The status of the pancreatic duct is the crucial point for management of pancreatic trauma and should be assessed as early as possible. Treatment has to be tailored to the individual situation, especially in patients with severe concomitant injuries or prolonged course.

Analysis of KIT (CD117) expression in gallbladder carcinomas by tissue microarray

AIMS

KIT (CD117) is a transmembrane tyrosinase-kinase receptor which has been related to cell proliferation, differentiation, adhesion and control of apoptosis. If present, KIT may provide a suitable target for tumour therapy. In this study, we report the presence of KIT in primary and metastatic gallbladder carcinomas.

METHODS

Formalin-fixed and paraffin-embedded specimens of 57 primary gallbladder carcinomas and 18 corresponding metastases were stained using a tissue microarray technique and two different antibodies.

RESULTS

Only three tumours stained for KIT. With a polyclonal antibody only one well differentiated papillary adenocarcinoma was immunoreactive. With a monoclonal antibody two additional poorly differentiated tubular adenocarcinoma showed weak and focal immunostaining.

CONCLUSIONS

KIT immunoreactivity is infrequent in gallbladder carcinoma. Thus, routine screening of tumour tissues for KIT by immunohistochemistry appears to be cost-ineffective and cannot be recommended. Moreover, the lack of substantial KIT immunoreactivity in both primary and metastatic gallbladder carcinoma tissues does not provide a rationale to investigate imatinib mesylate therapy in clinical trials including patients with advanced disease.

Post-methionine-load hyperhomocysteinemia and increased lipoprotein(a) are associated with renal metabolic dysfunction: a hypothesis

Previous studies have shown that homocysteine influences the structure of lipoprotein(a) [Lp(a)] and its affinity to fibrin, and that there is an increased risk of vascular disease when both homocysteine and Lp(a) are elevated. The aim of this study was to determine whether there is a correlation between increased total homocysteine (tHCY) and high Lp(a) concentrations, and whether increased concentrations of tHCY affect the concentration of unbound serum apolipoprotein(a) [Apo(a)]. Forty-seven male subjects recruited from a primary prevention screening program with normal serum creatinine and Lp(a) concentrations above 30 mg/dL were included and underwent a standardized oral methionine-loading test to increase the plasma tHCY concentration. This increase might lead to a modification of the Apo(a) structure, thus possibly influencing the serum concentration of unbound Apo(a). Fasting blood samples were taken before the tests and after 6 hours. The median values of tHCY increased about 4-fold after the methionine-loading test. Fasting tHCY did not show an association with Apo(a) and a post-methionine load increase of unbound Apo(a) was not observed. Backward multiple linear regression analysis, however, revealed that only post-load tHCY was independently and significantly influenced by Lp(a). Furthermore, Lp(a) correlated significantly with post-load tHCY, but not with fasting tHCY. Subdividing the subjects according to the Lp(a) concentration showed a significantly higher median concentration of tHCY after methionine load in subjects with Lp(a) over 50 mg/dL compared to subjects with Lp(a) under 50 mg/dL (P =.009). A similar cut-off was seen for post-load Apo(a) at 7.3 mg/dL (P =.04). Factors such as age, C677T-methylene-tetrahydrofolate-reductase (MTHFR) mutation, folate, vitamin B(12), and creatinine showed no significant influence on post-load tHCY in the different subgroups. The reasons for our findings remain partially unclear. However, considering our results and the current knowledge on the association of tHCY and Lp(a) concentration with the renal function, we hypothesize that both parameters may be linked by commencing renal metabolic dysfunction. It should be stressed that our hypothesis is speculative and that further studies will be necessary to improve the understanding of the interrelation of tHCY and Lp(a) concentration.